r-h regents chemistry - wikispacesadnychemistry.wikispaces.com/file/view/regents... · r-h regents...

1

R-H Regents Chemistry Miss Silsby

UNIT 6: Solutions – LEVEL 1

January 4 – 25, 2011

Focus Questions for the Unit: How can precise concentrations be made?

How are electrolytes described, in terms of formula, properties,

concentration, and pH?

YOU SHOULD BE ABLE TO ANSWER THESE IN DETAIL BY THE END OF THE UNIT

Name:

2

UNIT 6: Solutions

TABLE OF CONTENTS

Calendar ………………………………………………………………………….3

Vocabulary/Study Guide ………………………………………………………...5

Unit 6 Overview……..………………………………………………………......6

Topic 1: REVIEW – Types of Substances .………………………………….....7

Topic 2: Solubility of Ionic Compounds ………………………………………13

Topic 3: Concentration of Solutions ………………………………………......23

Topic 4: Electrolytes ………………….……………….. …………………......31

Topic 5: Properties of Acids and Bases..……………………………………......33

Topic 6: Acid-Base Neutralization Reactions …………………………..….......41

Topic 7: Acid-Base Titrations ……………………………………..…………...45

Regents Question Pack ………………………………………………………….48

Level 2 Bonus Work

Unit 6 Level 2 Bonus Work is being kept separate from the packet in order to conserve paper.

If you are interested in any of these assignments, check the class website and print only those

pages that you would like to do!

Appendix A: Topic 3 – Concentration of Solutions Text Problems ………………2

Appendix B: Topic 3 – Molarity Worksheet ……………………………………...3

Appendix C: Topic 3 – Molarity & Spectrophotometry (Lab Activity) …………..4

Appendix D: Topics 3 & 4 – Dissociation & Molarity ……………………………6

Appendix E: Topic 4 – Electrolytes Research Summary …………………………7

Appendix F: Topic 4 – Electrolytes Research …………………………………….8

Appendix G: Topic 7 – Titration Text Problems ………………………………….10

Appendix H: Topics 3, 4, & 7 – Dissociation, Molarity, & Titrations …………...11

3

January 2011 Sunday Monday Tuesday Wednesday Thursday Friday Saturday

2 3 4 5 6 7 8

F A B C D

9 10 11 12 13 14 15

E

ELA TEST (attend by

exam only) F A B

16 17 18 19 20 21 22

Martin

Luther King

Jr. Day

C D E F

23 24 25 26 27 28 29

A B

Mid Term

Exams

CHEM.

MID-

TERM

12:00 PM!

Mid Term

Exams

Grading Information:

Labs

Lab #6.1: Double Replacement Reactions & Table F

Lab #6.2: Acid-Base Properties

Quizzes

There will be two quizzes for this unit.

Quiz #1 - .

Quiz #2 - .

Testing

The topics within this unit will be tested on the midterm exam. No unit exam will be given!

Midterm

You should start budgeting your time so that you may prepare for the midterm exam.

4

Insert Your Day-Day Schedule Here

5

Unit 6 Study Guide: Solutions

Vocabulary: Topic 1: Review

□ Mixtures

o Homogeneous

o Heterogeneous

o Solutions

o Solute

o Solvent

Topic 2: Solubility

□ Precipitate

□ Dissociate

□ Soluble/Insoluble

Topic 3: Concentration

o Molarity

o Dilute

Topic 4: Electrolytes

Arrhenius theory

o Acid

o Base

o Salt

Topic 5: Properties of Acids/Bases

Acidity

o Hydronium ion

(= H+1

= H3O+1

ion)

o pH

Alkalinity

o Hydroxide ion (OH-1

ion)

Acid-Base Indicators

Topic 6: Acid-Base Neutralization

Acid vs. Base Reaction

o Neutralization

o Double Replacement

o Titration – Controlled

Neutralization

Lab Skills: By doing labs and interpreting & analyzing the results, you should be able to…

1. determine the formula of precipitates formed during double replacement reactions, using

Table F

2. classify solutions as acid, base, or neutral based upon the pH

3. identify substances as Arrhenius acids or Arrhenius bases based on properties

4. interpret changes in acid-base indicator color

5. identify a set of four unknown solutions

Reference Tables:

Table F – Solubility of Compounds

Table K & L – Names and Formulas of Common Acids & Bases

Table M – Acid-Base Indicator Information

Table T – Molarity, Gram Formula Mass (Molar Mass) and Titration Equations

Periodic Table – Atomic Masses

6

Unit 6 Overview:

7

Assignments: Text Reference p. 44-47 & p. 50

#1: Mixtures Review (Parts A, B, & C)

#2: Text Problems

**TOPIC 1**

REVIEW - TYPES OF SUBSTANCES

Assignment 1A: Mixtures (Review from Unit 1)

A solution is a homogeneous mixture where one

substance (the solute) is completely and evenly

dispersed in another substance (the solvent).

Making a solution is a physical change – if salt

is dissolved, it is still salt and the water is still

water. A phase is any part of a system with

uniform composition and properties. In a

homogeneous mixture such as a solution, there

is only one phase, meaning the components can

not be visually distinguished. A heterogeneous

mixture consists of more than one phase,

meaning the various components can be visually

distinguished.

Solutions are homogeneous mixtures in which

the solute will not settle out solution over time.

In solutions the solute exists as atoms, ions or

small molecules. Solutions can exist as solids

(alloys), liquids or gases. An alloy is a

combination of two metals.

Questions:

1. When a substance is dissolved is it a physical

or a chemical change? _____________________

_______________________________________

2. Why is a combination of metals the only solid

form of a solution? _______________________

_______________________________________

_______________________________________

Word Bank:

heterogeneous

homogeneous

mixture

phase

solute

solution

solvent

• A ______________________ is a physical combination of two or more pure substances.

• ________________________ mixtures have a uniform composition (e.g. salt water),

• ________________________ mixtures are not uniform in composition (a bucket of dirt).

• ________________________ is the material which is dissolved

• ________________________ is the material which “does the dissolving”

• ________________________ is the homogeneous mixture formed from a solute in a solvent

• ________________________ is any part of a system with a uniform composition

8

Assignment #1B: Separating Solutions (Some New & Some Review)

These are important when applied in your labs!

Mixtures can be separated by physical techniques. These include:

1. Phase changes

a. Evaporation of solvent leaving behind solute. (Evaporating a liquid leaving behind a solid.)

b. Distillation, which is a process where a liquid mixture is boiled to produce a vapor that is

condensed back into a liquid. This can remove the solids in water, such as tap water. This

process can also separate mixtures of two or more liquids which have different boiling

points.

2. Differences in solubility

a. Filtering insoluble solids from a solvent. (Filtering a solid from a liquid.)

Check for understanding:

1.) Why do we separate mixtures by physical and not chemical means (methods)?

2.) What is the difference between filtering based on solubility and filtering based on size/shape?

9

Assignment 1C: Putting it all Together

1. Fill in the blanks: • A mixture is a ________________ (physical or chemical) combination of two or more pure substances.

• ______________________ (heterogeneous or homogeneous) mixtures have uniform composition (ie salt water)

• ______________________ (hetero- or homogeneous) mixtures are not uniform in composition (bucket of dirt)

2. The Matter Flow Chart:

a) Complete this Flow Chart by placing these terms correctly:

compounds heterogeneous homogeneous elements

b) Then place “solutions” under the appropriate category (write under one of the four

lines below)

MATTER

Pure MIXTURES

SUBSTANCES of Substances

__________ _____________

______________ _______________

3. Complete the following. Read the previous page in your packet or p. 450 in your text if you

need help. Word Bank: (Words can be used more than once or not at all!)

sodium chloride

solute

solution

solvent

water

a. A solution is made of two parts. The substance that is doing the job of dissolving the other substance is called

the ______________________. The substance that is being dispersed, or dissolved, is called the

__________________________.

b. A solution is made using NaCl and water. In this case, the solute is the __________ and the solvent is the

________________.

c. Most solutions used by chemists are “aqueous” which means they are solutions where water is the

__________________.

d. Read the last paragraph on p. 450 carefully, maybe even more than once to make sure you understand.

Summarize by answering this… “What do the attractions between solute and solvent particles have to do with

whether or not a solute dissolves in a solvent?”

10

Assignment #2: Text Problems - p. 47 #13, 16, 17

p. 51 #18, 19

11

**TOPIC 1 CHECKPOINT/SELF-ASSESSMENT**

TYPES OF SUBSTANCES

You Should Know/Understand OR Be Able To:

1. Matter is classified as either a pure substance or a mixture of pure substances.

a. What are two examples of pure substances?

2. A pure substance (element or compound) has a constant composition and constant properties

throughout a given sample, and from sample to sample.

a. What does it mean to have a “fixed ratio” of elements?

3. Mixtures are composed of two or more substances that can be separated by physical means.

a. What are three physical methods that can be used to separate substances?

4. When substances are mixed together, either a homogeneous or heterogeneous mixture is

formed.

a. What is the difference between a homogenous and a heterogeneous mixture?

5. A solution is a homogeneous mixture of solute dissolved in a solvent.

a. What makes it a homogenous mixture and not a heterogeneous mixture?

Rate Your Understanding of Topic 1 on a scale of 1-10. ________

If you have mastered this topic, move on. If you have not mastered the topic, make sure

you did Assignments 1 & 2 and checked your answers. If you have done that either go back

and review these assignments, get help from a classmate, or schedule a homeroom

appointment.

Teacher’s Initials:

13

Assignments: Text Reference p. 451 & Good Pix on p. 472 & p. 560 #3: Dissociation of Ionic Compounds in Water

#4: Using Table F


**TOPIC 2**

SOLUBILITY OF IONIC COMPOUNDS

NOTES: Underline/highlight and write important ideas to the right using your own words.

Not all ionic compounds can dissolve or are

soluble in water. In order to decide, you will

learn how to use Table F!! Take a look now!

Substances that form in water stay dissolved

because they ARE soluble in water, while others

form “precipitates” and settle out as a solid

because they ARE NOT soluble.

Chemists use the word “dissociate” to describe

the falling apart process that a soluble ionic

compound undergoes. In other words, the ions in

the crystal are pulled apart by the action of water

molecules. Water molecules are able to pull ions

into solution by pulling on them with electrical

attractions. The oxygen end of a water molecule

has a somewhat negative charge to it, and thus

will be attracted to the positive ions in the salt

crystal. Conversely, the hydrogen side of water

molecules has a somewhat positive charge to it,

and is attracted to negative ions in the crystal.

The process of water molecules surrounding the

salt and dissolving it one ion at a time is called

“hydration.” The process of removing water to

make something return to a solid is called

“dehydration”.

You should learn how to write a “dissociation

equation.” Here are a couple examples:

H2O

LiBr(s) Li+1

(aq) + Br-1

(aq) H2O

Na2SO4(s) 2 Na+1

(aq) + (SO4)-2

(aq)

What do we notice about these examples?

14

Assignment #3: Dissociation of Ionic Compounds in Water

Here is the picture found on page 472. It will be

helpful to look at the textbook to see it in color.

Summarize what is happening in the picture:

__________________________________________

__________________________________________

__________________________________________

__________________________________________

__________________________________________

Answer the question that is asked in the caption:

__________________________________________

__________________________________________

__________________________________________

__________________________________________

Now take a look at the picture found on page 560.

It will be helpful to look at the textbook to see it

in color. (Remember to look in the assignment box

at the beginning of each topic for helpful textbook

pages and pictures!)

Figure 18.16 Silver chloride is slightly soluble in

water.

Summarize what is happening in the picture:

__________________________________________

__________________________________________

__________________________________________

__________________________________________

__________________________________________

__________________________________________

__________________________________________

15

Assignment #3 CONTINUED: Dissociation of Ionic Compounds in Water

A Closer Look: How do ionic compounds dissociate in water?

“Dissociate” is a shortened up form of “dis-associate”. If an ionic compound dissolves in water,

it is because the attraction of water molecules for the ions is able to pull the ions apart from each

other, overcoming their ionic bonds and causing them to “dis-associate” from each other.

Read p. 451 and study the pictures on the previous page.

Your teacher will show you an animation of sodium chloride dissolving in water. Describe or

draw your observations:

Is the action of one or several water molecules needed to pull an ion out of its crystal?

Draw pictures showing how water molecules will orient themselves when surrounding these ions. The

Hydrogen ends of water molecules are + charged and the Oxygen end is – charged. It is useful to draw

water like this:

Complete the “dissociation” equations below by putting correct numbers on each blank.

Study the HCl example on p. 453 and/or the NaOH and KOH examples on p. 589. The bottom

half of Table I will be helpful as well. Here’s an additional example:

H2O K3(PO4) (s) 3 K+1 (aq) + 1 (PO4)

3- (aq)

H2O

1. ____ NaI (s) ___ Na+1 (aq) + ___ I 1- (aq)

H2O

2. ____ Na2S (s) ___ Na+1 (aq) + ___ S 2- (aq)

H2O

3. ____ CaCl2 (s) ___ Ca+2 (aq) + ___ Cl 1- (aq)

H2O

4. ____ Ca3(PO4)2 (s) ___ Ca __+ (aq) + ___ PO4

__- (aq)

K1+

S2-

16

Assignment #4: Using Table F (If you need help remembering how to turn names into formulas, just write the formula and check it before you

go on to determining its solubility.)

Part A Directions: Part B Directions:

a.) Write the chemical formula. Write a dissociation equation for

b.) Determine if it is soluble or insoluble in water. each of the SOLUBLE compounds.

1) Lithium bromide

a.)

b.)

2) Potassium hydroxide

a.)

b.)

3) Silver nitrate

a.)

b.)

4) Silver iodide

a.)

b.)

5) Sodium acetate

a.)

b.)

6) Aluminum phosphate

a.)

b.)

7) Why can’t you write dissociation equations for insoluble compounds?

17


Lab Question: How can you determine the identity of a precipitate when a double replacement

reaction happens?

Introduction: When two substances undergo a chemical reaction, new substances form. One type

of reaction, a double replacement reaction (AB + CD AD + CB) can form soluble

or insoluble products. In this lab we will try to find out how the solubility of a

substance (aqueous or precipitate) can be determined when a double replacement

reaction happens.

Pre-Lab: Answer the following questions.

1.) Which of the following reactions would be classified as a double replacement reaction?

(1) 2 Mg + O2 2 MgO Explain your choice:

(2) 2 NH3 N2 + 3 H2

(3) Zn + 2 HCl ZnCl2 + H2

(4) NaOH + HCl NaCl + HOH

2.) What is a “precipitate”? If you mix two solutions, how do you know if a precipitate has formed or

not? (Review the notes on p. 13 of this unit booklet for help!)

3.) A student chemist performs the following reaction and observes a precipitate forming as the

reactant solutions are mixed.

3 Ag(NO3) (aq) + Na3(PO4) (aq) Ag3(PO4) (s) + 3 Na(NO3) (aq)

a.) Which product is the precipitate?

b.) What clue in the reaction tells you that this substance is the precipitate?

Lab: Safety:

WEAR YOUR SAFETY GOGGLES!

Silver nitrate (AgNO3) will stain your skin with black spots.

All of the solutions and products are toxic by ingestion. Make sure to WASH YOUR HANDS

when you are done with this lab!

18

Procedure: 1.) Use a well plate to observe the reactions between pairs of the following solutions of ionic

compounds.

2.) Set up the well plate as shown in the “OBSERVATIONS” section below.

3.) Mix solutions as shown on the well plate “map,” using white paper beneath.

Observations: 1.) Do each of the six reactions as shown below. (They are labeled as Reactions A – F.)

2.) If no observable reaction happens, put “N.R.” (No Reaction) in the circle for that reaction.

3.) If a reaction happens, you will see a precipitate. Put “PPT” (Precipitate) in the circle, note the

color of it, and if bubbles formed. (You may need to pick up the well plate carefully and look

underneath it to make some of these observations!)

4.) When done, dump the contents of the well plate into the white waste container under the fume

hood, and then thoroughly wash the plate to remove all residues.

5.) WASH YOUR HANDS when you have completed clean up!

Reaction A Reaction B Reaction C

Reaction D Reaction E

Reaction F

empty

1 AgNO3

supply

2 Pb(NO3)2

supply

4 K2CrO4

supply

3 CuCl2

supply

1 & 2

empty

2 & 3

1 & 3

3 & 4

2 & 4

1 & 4

19

Post-Lab Analysis:

1.) Circle the following reactions that resulted in a “PPT.”

Reaction A Reaction B Reaction C

Reaction D Reaction E Reaction F

2.) For EACH of the FIVE reactions that formed a precipitate:

1- Determine the chemical formulas of your products

2 – Write the chemical equation.

3 – Balance the equation.

4 – Put phases in for each of the reactants and products. Use Table F to decide which of your two

products was the precipitate!

5 – Circle the product that is the precipitate.

(There is room for you to do this on the next page…)

Example: If we mixed solutions of Pb(NO3)2 and KI and observed a “PPT”…

Step 1: Determine the chemical formulas of your products.

Pb2+

I1-

PbI2 K1+

(NO3)1-

K(NO3)

Step 2: Write the chemical equation.

Pb(NO3)2 + KI K(NO3) + PbI2

Step 3: Balance the equation.

1 Pb(NO3)2 + 2 KI 2 K(NO3) + 1 PbI2

Step 4: Put phases in for each of the reactants and products.

1 Pb(NO3)2 (aq) + 2 KI (aq) 2 K(NO3) (aq) + 1 PbI2 (s)

We started with 2 solutions Table F says “soluble” Table F says “insoluble”

Step 5: Circle the precipitate.

1 Pb(NO3)2 (aq) + 2 KI (aq) 2 K(NO3) (aq) + 1 PbI2 (s)

Think about it! Why is it not beneficial to write the double replacement for the reaction that did not

produce a precipitate?

20

Complete Steps 1& 2, have your teacher check them, and THEN move on with Steps 3-5!

Hint… USE A PENCIL!

Reaction :

Reaction :

Reaction :

Reaction :

Reaction :

Challenge: Have your teacher show you how to use the CRC Manual to look up the “accepted” colors of your

precipitates. How did you do? Analyze your results compared to that of the CRC Manual.

21


SOLUBILITY OF IONIC COMPOUNDS


6. Some ionic compounds are soluble in water and others are not.

a. How can you determine which compounds dissolve in water and which do not?

7. Ionic compounds that do not dissolve are said to be insoluble.

a. Does this mean that the attraction between ions is greater or is the attraction of ions for

water greater?

8. Use Table F in order to determine in an ionic compound is soluble or insoluble in water.

a. Name one compound that does NOT dissolve in water.


If you have mastered the material in Topic 2, move on. If you have not, you know what to

do to fix this!!! (If you don’t, ask the teacher!)


23

Assignments: Text Reference Section 16:2 p. 480-482 (STUDY THE EXAMPLES!)

#5: Qualitative Concentrations: Dilute v. Concentrated

#6: Quantitative Concentrations: Molarity

#7: Text Problems

**TOPIC 3**

CONCENTRATION OF SOLUTIONS

Solutions are made when one substance is SOLUBLE in another and dissolves.

Scientists have to come up with terms that qualitatively and quantitatively describe the

amount of the two substances, solute and solvent (see Assignment 1 for these definitions if

you don’t remember them), that are present in each solution.

This topic contains “new info” but is probably familiar based on your life experiences.

Important VOCABULARY:

Concentration is a measurement of the amount of a solute that is dissolved in a given amount of a

solvent. Concentration can be abbreviated [ ].

Qualitative: Two qualitative ways of describing the concentration of solutions are to use the terms

“dilute” and “concentrated”.

• Dilute solutions are solutions which have a small amount of solute dissolved as compared to the

amount of solvent.

• Concentrated solutions have a lot of solute dissolved as compared to the amount of solvent.

Check for Understanding: Brainstorm examples from your life where you have dealt with different concentrations of

substances. When you are done, explain how you could have made these solutions more dilute or

concentrated.

24

Assignment #5: Qualitative Concentration (Remember to concentrate while you work )

1. Look at the Picture below:

Which of the two solutions is more concentrated

with solute particles? How do you know?

_________________________________________

_________________________________________

_________________________________________

2. In each pair below, circle the solution which is more concentrated:

A) 10 grams of sugar dissolved in 50 mL of solution, OR

20 grams of sugar of dissolved 50 mL of solution

B) 1.3 moles of NaCl dissolved in 100 mL of solution, OR

1.7 moles of NaCl dissolved in 100 mL of solution

C) 1.3 moles of NaCl dissolved in 100 mL of solution, OR

1.3 moles of NaCl dissolved in 200 mL of solution

3. Summarize: What does the word “concentrated” mean, in terms of the relative amounts of

solute and solvent particles?

__________________________________________________________________________

__________________________________________________________________________

Refer to p. 480-482 in the textbook to answer questions 4 & 5.

4. What does the word “concentrated” mean?

__________________________________________________________________________

5. What does the word “dilute” mean?

__________________________________________________________________________

25

Assignment #6A: Quantitative Concentration Guided Notes

Quantitative:

The terms dilute and concentrated are scientifically inexact terms. Scientists like to

be very exact or precise with their measurements. In other words, we like to be very

close to the actual numerical value. These terms do not give us numbers so scientists

use a calculation to find the concentration of particles. This calculation is called

MOLARITY.

Molarity is the preferred method of chemists to measure concentration.

(Other ways are “% mass”, which is preferred by biologists and those in the medical sciences,

and “part per million” which is preferred in the environmental sciences.)

Molarity (M) is concentration expressed as moles of solute per liter of solution (mol/L).

M = units are M or (mol/L)

This is found on Reference Table _______________.

Working with this equation requires us to review a couple of things:

1) In order to get the moles of solute we need to be able to do:

a) Molar Mass/Gram Formula Mass:

Calculate the Molar Mass of the compound Na2SO4.

b) Mass-Mole Converting:

Calculate the # of moles represented by 50 g of Na2SO4.

2) Volume is always expressed in liters, never in mL so we need to be able to convert.

Remember that: 1000 mL = 1 L

Convert the following volumes in milliliter to liters:

2500 mL = _______ L 250 mL = _______ L 25 mL = _______ L

moles of solute

liters of solution

26

Here are some EXAMPLES of calculating with Molarity:

1. What is the molarity (M) of a solution which has 2.5 moles of solute in enough water to

form .75 L of solution?

Answer: M = moles = 2.5 mol = 3.3 M

L .75 L

2. What is the molarity of a solution formed by dissolving 5.5 g of NaCl in enough water to form

1.2 L of solution?

(Sometimes if the problem only gives you grams, you may need to calculate the number of

moles first as shown here).

First calculate the number of moles of NaCl. In order to do this we must first calculate the

molar mass and then convert that into moles. (Molar Mass of NaCl=58.5g/mol)

5.5 g x 1 mole = 0.094 moles

58.5 g

Now determine the concentration: M = moles = 0.094 moles = 0.078 M

L 1.2 liters

3. How many moles of NaCl are in 3 liters of a 0.5 M solution?

(Sometimes only Molarity and liters are given to us and we will need to solve for moles.)

M = moles 0.5 M = x moles 0.5 M = x moles x = 1.5 moles L 3 L 1 3 L

Cross multiply and solve for x!

27

Assignment #6B: Quantitative Concentration- Using the Molarity Equation

Concentration is often expressed as “Molarity” (M) or moles per liter (moles/liter).

M = moles of solute .

liters of solution

(NOTE: 1000 mL in 1 Liter)

Directions: Calculate the odd problems first… do the evens if you need more practice.

1. Concentration of 1 mole of HCl in 0.50 Liters of water.

2. Concentration of 0.5 moles of NaCl in 2.0 Liters of water.

3. Concentration of 0.125 moles of NaOH in 300 mL of water.

4. Number of moles of KBr in 10 Liters of 0.01M solution.

5. Number of moles of HBr in 125 mL of 1.25M solution.

28

6. Number of Liters of 0.10 M HCl required to give 4.2 moles.

7. Number of Liters of 2.5M NaOH required to give 1.5 moles.

8. Number of mL of 0.120 M solution of KOH to give 0.0165 moles.

9. What is the Molarity when 83 grams of NaOH are dissolved to make 325 mL of solution?

Challenge: On a separate sheet of paper (to be turned in) explain how you would make the

following solution. You should tell how many grams of the substance you need to

make the solution, not how many moles. You will need to calculate moles first,

though.

1.5 L of a 2.0 M NaOH solution

29

Assignment #7: Text Problems - p. 468 #7

p. 499 #56

30

**TOPIC 3 CHECKPOINT/SELF-ASESSMENT**

CONCENTRATION OF SOLUTIONS


9. The word “concentration” describes how much solute has been dissolved in the solvent.

a. Does a high concentration indicate a lot or a little solute has been dissolved in solvent?

10. Solutions are sometimes described as “dilute” or “concentrated.”

a. Which of these terms indicates that a lot of H2O has been added?

b. Are solutions homogenous or heterogeneous mixtures?

11. One way chemists describe concentration is to express it as molarity (M).

a. Why does molarity have to be represented by a capital (M) and NOT a lowercase (m)?

12. Calculate solution concentration in molarity (M).

a. Where can you find the formula to calculate Molarity?

b. What formula is used to calculate molarity?

13. Describe how to prepare a solution, given the molarity desired

a. Describe how to make a 2L solution of 4M hydrochloric acid.


If you have mastered the material in Topic 3, move on. If you have not, you know what to do to

fix this!!! (If you don’t, ask the teacher!)


31

Assignments: Text Reference p. 452-453, 588-589, & Good Pix on p. 488 #8: Text Problems

PART 1 of Lab #6.2: Acid-Base Properties

**TOPIC 4**

ELECTROLYTES

The lab is broken up into four parts. Each part corresponds with the next four topics. You can either start with

the lab OR the assignments but make sure that you realize they are interconnected (don’t just do all the

assignments and then the lab or just do the lab then do the assignments). You should think about your learning

style in order to make this decision… what helps you learn best?

MINI-LESSON:

Here is the picture from p. 488… it may help to look at it in color in your textbook too!

For ionic compounds that dissolve in water, describing them as “electrolytes” is appropriate, since the

crystal will fall apart in water. An electrolyte is a substance that dissolves in water and forms a

solution capable of conducting an electric current. The ability of a solution to conduct an electric

current depends upon the concentration of ions that are present.

Look at the picture above. Write out the formula for each compound.

Glucose = Sodium Chloride = Calcium Chloride =

Which would be the best electrolyte (strongest conductor)? ______________How do you know?

What types of particles must be present in a solution if it is to conduct electricity?

Why does molten sodium chloride conduct electricity?

32

What Exactly Makes Something An Electrolyte?

First off, if a substance is referred to as an “electrolyte,” then it must be able to dissolve in water.

Secondly, when it does dissolve, it forms ions in solution. As a result it can conduct electricity. “-Lyte”

is Latin for “break”, and “electro-“ is Latin for “electricity.” Putting that all together then, an “electro-

lyte” is a substance that “breaks” into ions when dissolved in water, and as a result, conducts

“electricity.”

3 Types of Electrolytes: Electrolytes are classified according to the type of ions formed by the substance when it dissolves.

Svante Arrhenius was a Swedish chemist who first studied this branch of chemistry, and developed the

following categories:

1. Arrhenius Acid – a substance that dissolves to form H+1

ion as the ONLY positive ion in solution.

2. Arrhenius Base - a substance that dissolves to form (OH)-1

ion as the ONLY negative ion in

solution.

3. Salts – a substance that dissolves to form a positive ion other than H+1

and a negative ion other

than (OH)-1

Check for understanding… are salts ionic or covalent compounds? ____________

Examples:

Dissolving in water Type of electrolyte Why? 1. HCl(s) H

+1(aq) + Cl

-1 (aq) acid H

+1 is the only positive

ion in solution

2. NaOH(s) Na+1

(aq) + (OH)-1

(aq) base (OH)-1

is the only

negative ion in solution

3. K(NO3)(s) K+1

(aq) + (NO3)-1

(aq) salt Positive and negative ions

other than H+1

and (OH)-1

are present

4. NH3(aq) NH4+1

(aq) + (OH)-1

(aq) base (OH)-1

is the only

negative ion in solution

33

Assignment #8: Text Problems - p. 466 #64

p. 468-469 #5, 21-23 ** Don’t skip these…**

p. 625 #44, 45

p. 628 #3, 5

34


ELECTROLYTES


14. An electrolyte is a substance that dissolves in water and forms a solution capable of

conducting an electric current. The ability of a solution to conduct an electric current

depends upon the concentration of ions present.

a. What is the relationship between concentration of ions and conductivity?

15. Arrhenius acids and bases are electrolytes. Soluble salts are also electrolytes.

a. These substances all have a positive and a negative ion. Why is this characteristic

necessary for something to be an electrolyte?

16. Sort compounds as Arrhenius acids, Arrhenius bases, or salts according to their chemical

formulas.

a. Which category does Ca(OH)2 belong in? How do you know?




Teacher’s Initials: ______

35

Assignments: Text Reference p. 587-588

#9: Acid-Base Properties

PART 2 of Lab #6.2: Acid-Base Properties

**TOPIC 5**

PROPERTIES OF ACIDS & BASES

Notes: Acid & Base Properties:

Acids dissociate in water to form H

+1 ions (sometimes referred to as H3O

+1 or “hydronium” ion).

Example: HCl is a monoprotic acid because when it is dissolved in water 1 mole of H+1

ions are

present.

Monoprotic: mono means 1, protic for “proton” or H+1

ion

There are also diprotic, triprotic, etc. acids depending on how many moles of H+1

ions are

present in solution

Examples:

HCl H+1

+ Cl-1

monoprotic acid ( = 1 H+ ion produced)

H2(SO4) 2 H+1

+ (SO4)2-

diprotic acid ( = 2 H+ ions produced)

Check for understanding… if a solution is acidic, what ion is causing this property? _____

Bases dissociate in water to form the hydroxide ion, (OH)-1

.

Base Example: Na(OH) is a monohydoxy base because when it is dissolved in water 1 mole of

(OH)-1

ions are present in solution.

Monohydroxy: mono means 1, hydroxy for “hydroxide ion”

There are also dihydroxy, trihydroxy, etc. bases depending on how many moles of (OH)-1

ions are present in solution

Examples: NaOH Na

+1 + OH

-1 monohydroxy base ( = 1 OH

- ion produced)

Ca(OH)2 Ca2+

+ 2 OH-1

dihydroxy base ( = 2 OH- ions produced)

Check for understanding… if a solution is alkaline, what ion is causing this property? ____

36

Notes: Table M & Common Acid-Base Indicators

The properties that an acid displays are due to the presence of H+1

ions, and the properties of

bases are due to (OH)-1

ions. There are different categories of acids and bases depending on how

many H+1

or (OH)-1

ions are present in solution. We use indicators to measure the level of

H+1

ions in a solution.

Acid-base indicators are molecules that are natural dyes, and these dyes happen to be sensitive to pH

changes, such that they take on different colors depending on the pH.

If you look at Table M in your Reference Tables, you will notice some indicators listed.

Look at bromothymol blue. Read the info like this… if the indicator is put into a solution and it turns

yellow, then we know the pH is 6 or less. If it turns blue, the pH is 7.6 or higher. Some indicators have

an in-between color as well. Bromothyml blue turns green if the pH is between 6 and 7.6.

For each acid-base indicator on Reference Table M, color the chart below to indicate appropriate color of

the indicator from pH 1to 14.

pH 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Methyl orange

Bromthymol blue

Phenolphthalein

Litmus

Bromcresol green

Thymol Blue

Check for understanding:

1.Which indicator is blue in a neutral solution?________________

2. Name an indicator that is yellow at pH 4.__________________

3. Name an indicator that is yellow at pH 9. __________________

4. What is the pH of a solution that changes methyl orange indicator yellow and litmus red?

__________________

5. Which indicator appears colorless in HNO3? ________________

6. Bromcresol green indicator is added to a beaker containing NaOH. What color change will be

observed as HCl is added to the solution in the beaker?_______________________________

37

Assignment #9: Acid-Base Properties (Don’t forget to check the text references to see what pages in the text can help you with each assignment!)

1. Compare acids and bases by completing the table.

Property Acid Base

Electrolytes?

(Yes or No)

Taste

Effect on Methyl Orange Indicator

(See Table M)

Reacts with metals?

(Yes or No)

Feeling when touched

Contained in which common

household products?

2. For each: (USE TABLE K AND L To Convert NAMES of Acids or Bases to Formulas)

o classify the reactant as an acid or a base,

o indicate what type of acid or base (monoprotic, dihydroxy, etc.)

o write the equation for its dissociation (ionization) when dissolved in water.

Classify Type Dissociation Equation Applications Acid Monoprotic a. H(NO3) H

+ + (NO3)

- (Nitric Acid)

________ ____________ b. Hydrochloric Acid (“Muriatic” acid)

________ ____________ c. HBr (Hydrobromic Acid)

Base Monohydroxy d. Na(OH) Na+ + (OH)- (Sodium Hydroxide – “Lye”)

________ ____________ e. Potassium hydroxide

________ Diprotic f. Sulfuric Acid (“Battery” acid)

________ ____________ g. H2C2O4 (Oxalic Acid – Rhubarb)

________ Dihydroxy h. Ba(OH)2 (Barium Hydroxide)

________ ____________ i. Calcium Hydroxide (“Lime”)

________ ____________ J. Phosphoric Acid (found in Coke and Pepsi)

________ ____________ k. Al(OH)3 (found in TUMS & ROLAIDS)

38

MINI-LESSON: The Meaning of pH

pH stands for “parts Hydrogen”. (Notice that the H must be capital!)

Solutions that are acidic have pH values less than 7 in value. Alkaline solutions are basic, so they have

pH values greater than 7. An acidic solution has more H+1

ions in it than (OH)-1

ions. The opposite is

true of basic solutions. “Neutral” solutions contain an equal number of H+1

ions and (OH)-1

ions and

have a pH value of 7.

As pH decreases, the concentration of H+ increases

As pH changes by one unit, [H+] changes by a factor of 10 (pH is a logarithmic scale)

A pH of 5 compared to a pH of 6: A pH of 5 is 10 times more acidic.

A pH of 8 compared to a pH of 5: A pH of 5 is 1000 times (10 x 10 x 10) less acidic.

pH Practice

1. Given pH in the chart below, fill in the other two columns.

pH Value [H+] in scientific notation [H

+] as a decimal value

1 10-1

Molar 0.1M

2 10-2

Molar 0.01M

7 10-7

Molar 0.0000001M

9 10-9

Molar 0.000000001M

2. A solution with a pH = 1 is _______ times more concentrated in [H

+] than a solution with a pH = 2.

3. A solution with a pH = 4 is _______ times less concentrated in [H


4. A solution with a pH = 2 is _______ times ______ concentrated in [H


5. Given a solution with a [H

+] = 1.0 x 10

-6 Molar, what would be the pH of a solution that is 1000 times

more concentrated in [H+]?

39

Summary: Properties of Acids & Bases

Complete the following Venn Diagram using the terms below.

40


PROPERTIES OF ACIDS & BASES


17. Behavior of many acids and bases can be explained by the Arrhenius theory.

a. What properties of acids and bases determine this behavior?

18. The acidity or alkalinity of a solution can be measured by its pH value.

a. Does a higher or lower pH indicate an alkaline solution?

19. The relative level of acidity or alkalinity of a solution can be shown by using indicators.

a. What table on your reference table lists these indicators?

20. Arrhenius acids yield H3O+ (hydronium ions) as the only positive ions in an aqueous solution.

a. Give an example of an Arrhenius acid.

21. Arrhenius bases yield OH- (hydroxide ions) as the only negative ions in an aqueous solution.

a. Give an example of an Arrhenius base.

22. Given properties, identify substances as Arrhenius acids or Arrhenius bases.

a. What is the difference between an Arrhenius acid or Arrhenius base?

23. Identify solutions as acid, base, or neutral based upon the pH.

a. What does a pH of 7 indicate? ________ 3? ________ 11? __________

24. Interpret changes in acid-base indicator color.

a. Methyl orange indicator is placed into a solution and turns red. What is a possible pH of

this solution?





41


#10: Classifying Solutions

#11: Neutralization Reactions

Pre-Lab to PART 3 of Lab #6.2: Acid-Base Properties

**TOPIC 6**

ACID-BASE NEUTRALIZATION REACTIONS

This topic is something you have probably heard of!

We are going to connect the idea of pH to the skill of writing and balancing equations.

Remember this picture from the front of the packet?

What do you think it means?

When an acid neutralizes a base, the products are always a salt and

water.

If you think about this, it all makes sense… the thing that makes a

solution acidic is the presence of H+1

ions, and the thing that makes a

solution a base is the presence of (OH)-1

ions. Therefore, when these

two types of solutions are mixed, these two oppositely charged ions

attract and bond together to make water molecules. Since there are

no longer any acid ions or base ions around, the pH would be 7, or

NEUTRAL, hence being described as a neutralization reaction!

A neutralization reaction is a double replacement reaction. You should be able to write a reaction if

you know the acid and base involved, since, as mentioned above, a salt and water are always formed.

For example: Na(OH) + H(NO3) Na(NO3) + H(OH)

base acid salt water

Your turn: H2SO4 + 2 NaOH 2 HOH + Na2(SO4) Label each chemical as

acid, base, salt, or water.

Summary: To determine if a reaction is neutralization, look to see if an acid and base is

reacting in a double replacement reaction to produce salt and water.

42

Assignment #10: Classifying Solutions

Model:

Key Questions:

1. How does the concentration of H+

compare to the concentration of OH─

in solution A?



in solution B?



in solution C?

4. Identify the acidic solution in the model.

5. Identify the basic solution in the model.

6. Identify the neutral solution in the model.

Exercises:

1. Based upon the information presented in the key of the Model, draw reactants and products that form

when an H+

ion is added to an OH─

ion.

2. What would happen if solution A and solution B were mixed? Explain your answer.

3. Classify the solution that forms in Exercise 2 (when solution A & B are mixed) as acidic, basic, or

neutral. Justify your classification in terms of the concentration of H+

ions and OH─

ions.

4. Can a neutral solution contain H+

and/or OH─

ions? Explain.

43

Assignment #11: Neutralization Reactions

When an acid reacts with a base, a salt and water are formed.

A salt is the general name for an ionic compound.

HCl + NaOH

H2O +

NaCl

HBr

+

KOH

H2O + KBr

HNO3 + NaOH H2O + NaNO3

H2SO4 + 2 KOH 2 H2O + K2SO4 ( note the diprotic acid)

2 HNO3 + Mg(OH)2 2 H2O + Mg(NO3)2 (note the dihydroxy base)

A neutral solution is formed when the right number of moles of strong acid reacts with strong base.

Directions: Write the products and balance the equation for each of the following reactions.

Example: 2 HBr + 1 Mg(OH)2 1 MgBr2 + 2 H2O

1. ___ HNO3 + ___ KOH

2. ___ H2SO4 + ___ NaOH

3. ___ HCl + ___ LiOH

4. __H2SO4 + ___ KOH

5. ___ HI + ___ Ca(OH)2

6. What type of chemical reaction are neutralization reactions? ______________________ (Synthesis, Decomposition… etc.)

44


ACID-BASE NEUTRALIZATION REACTIONS


25. In the process of neutralization, an Arrhenius acid reacts with an Arrhenius base.

a. What two products are ALWAYS formed? (This is how I tell if it is a neutralization

equation).

b. Label each compound in the following reaction as an acid, base, salt, or water.

HCl + NaOH NaCl +H2O

26. Write simple neutralization reactions when given the reactants.

a. Complete the following reaction…

H2SO4 + NaOH





45


#12: Acid-Base Titrations

Finish PART 3 of Lab #6.2: Acid-Base Properties

**TOPIC 7**

ACID-BASE TITRATIONS

NOTES:

A “titration” is a controlled neutralization done by adding small amounts (“titre” is another word for “a

small amount”). It is done in the laboratory by mixing a volume of a solution of known concentration

with a volume of a solution of unknown concentration, until neutralization occurs. We know

neutralization has occurred by a color change. The purpose is to determine the unknown

concentration.

One unit of H1+

is required to wipe out (neutralize) one unit of (OH)1-

.

You will be doing a similar procedure to the diagram above in the lab, except you will not need to use

the apparatus above. You will simply add and record specific amounts of each an acid and a base to a

well plate until you observe a color change.

46

# moles = Molarity x Volume (# moles = M•V)

Therefore, in a neutral solution: MAVA = MBVB

(where MA = molarity of hydrogen ion, VA = volume of acidic solution,

MB = molarity of hydroxide ion, and VB = volume of basic solution)

Assignment #12: Acid-Base Titrations

In a neutral solution, the moles of H+ = moles of OH

−

1.) How many moles of H+ ions are present in one liter of 2 M HCl?

2.) How many moles of OH− ions are needed to completely neutralize one liter of 2 M HCl?

3.) How many moles of OH− ions are present in one liter of 0.5 M NaOH?

4.) How many moles of H+ ions are needed to completely neutralize one liter of 0.5 M NaOH?

5.) How many moles of OH− ions are needed to completely neutralize 0.50 liter of 2 M HCl?

6.) How many mL of 2.0 M NaOH are required to exactly neutralize 100. mL of 3.0 M solution of HBr?

7.) How many mL of 2.0 M HBr are needed to exactly neutralize 20. mL of 4.0 M KOH?

8.) If 50.0 milliliters of 3.0 M HNO3 completely neutralized 150.0 mL of KOH, what was the molarity of

the KOH solution?

47


ACID-BASE TITRATIONS


27. Titration is a laboratory process in which the volume of a solution of known concentration is

used to determine the concentration of another solution.

a. What two types of solutions must be used for a titration to work? (Hint: Topic 7 Title)

28. Calculate the concentration or volume of a solution, using titration data.

a. Where can you locate the titration equation?

c. What is the titration equation?

d. How many mL of 2.0 M Mg(OH)2 are required to exactly neutralize 100 mL of 3.0 M

HBr?





48

Assignment #13: REGENTS QUESTION PACK

Types of Substances:

1. Which physical property makes it possible to separate the components of crude oil by means of distillation?

(1) melting point (2) conductivity (3) solubility (4) boiling point

2. One similarity between all mixtures and compounds is that both:

(1) are heterogeneous (3) combine in a definite ratio

(2) are homogeneous (4) consist of two or more substances

3. When a mixture of water, sand, and salt is filtered, what passes through the filter paper?

(1) water, only (3) water and salt, only

(2) water and sand, only (4) water, sand, and salt

4. Which must be a mixture of substances?

(1) solid (2) liquid (3) gas (4) solution

Solubility:

1. Which of the following compounds is least soluble in water?

(1) copper (II) chloride (3) iron (III) hydroxide

(2) aluminum acetate (4) potassium sulfate

2 Based on Reference Table F, which of these salts is the best electrolyte?

(1) sodium nitrate (3) silver chloride

(2) magnesium carbonate (4) barium sulfate

3. What is the correct IUPAC name for the compound NH4Cl?

(1) nitrogen chloride (3) ammonium chloride

(2) nitrogen chlorate (4) ammonium chlorate

4. Based on Reference Table I, which change occurs when pellets of solid NaOH are added to water and stirred?

(1) The water temperature increases as chemical energy is converted to heat energy.

(2) The water temperature increases as heat energy is stored as chemical energy.

(3) The water temperature decreases as chemical energy is converted to heat energy.

(4) The water temperature decreases as heat energy is stored as chemical energy.

5. What is the correct formula for iron (III) phosphate?

(1) FeP (2) Fe3P2 (3) FePO4 (4) Fe3(PO4)2

6. Given the equation: KNO3(s) + H2O(l) KNO3(aq)

As H2O(l) is added to KNO3(s) to form KNO3(aq), the entropy of the system

(1) decreases (2) increases (3) remains the same

Use this info for #7 & 8:

Given the equation for the dissolving of sodium chloride in water: NaCl(s) + H2O Na+(aq) + Cl

–(aq)

7. Describe what happens to entropy during this dissolving process.

8. Explain, in terms of particles, why NaCl(s) does not conduct electricity.

49

Use this info for #9 - 11:

Potassium ions are essential to human health. The movement of dissolved potassium ions, K+(aq), in and out of a

nerve cell allows that cell to transmit an electrical impulse.

9. What is the total number of electrons in a potassium ion?

10. Explain, in terms of atomic structure, why a potassium ion is smaller than a potassium atom.

11. What property of potassium ions allows them to transmit an electrical impulse?

Molarity: 1. How many moles of solute are contained in 200 milliliters of a 1 M solution?

(1) 1 (2) 0.2 (3) 0.8 (4) 200

2. What is the total number of grams of NaI(s) needed to make 1.0 liter of a 0.010 M solution?

(1) 0.015 (2) 0.15 (3) 1.5 (4) 15

3. What is the molarity of a solution of NaOH if 2 liters of the solution contains 4 moles of NaOH?

(1) 0.5 M (2) 2 M (3) 8 M (4) 80 M

4. What is the molarity of a solution containing 20 grams of NaOH in 500 milliliters of solution?

(1) 1 M (2) 2 M (3) 0.04 M (4) 0.5 M

Acids & Bases: 1. Which substance is an Arrhenius acid?

(1) LiF(aq) (2) HBr(aq) (3) Mg(OH)2(aq) (4) CH3CHO

2. When 50. milliliters of an HNO3 solution is exactly neutralized by 150 milliliters of a 0.50 M solution of

KOH, what is the concentration of HNO3?

(1) 1.0 M (2) 1.5 M (3) 3.0 M (4) 0.5 M

3. When the pH of a solution changes from a pH of 5 to a pH of 3, the hydronium ion concentration is

(1) 0.01 of the original content (3) 10 times the original content

(2) 0.1 of the original content (4) 100 times the original content

4. A sample of Ca(OH)2 is considered to be an Arrhenius base because it dissolves in water to yield

(1) Ca2+

ions as the only positive ions in solution

(2) H3O+ ions as the only positive ions in solution

(3) OH– ions as the only negative ions in solution

(4) H– ions as the only negative ions in solution

5. Which reaction occurs when hydrogen ions react with hydroxide ions to form water?

(1) synthesis (2) titration (3) decomposition (4) neutralization

50

6. Four flasks each contain 100 milliliters of aqueous solutions of equal concentrations at 25°C and 1 atm.

a. Which solutions contain electrolytes?

b. Which solution has the lowest pH?

c. What causes some aqueous solutions to have a low pH?

d. Which solution is most likely to react with an Arrhenius acid to form a salt and water?

7. Which equation represents a double replacement reaction?

(1) 2 Na + 2 H2O 2 (3) LiOH + HCl LiCl + H2O

(2) CaCO3 + CO2 (4) CH4 + 2 O2 CO2 + 2 H2O

8. The only positive ion found in an aqueous solution of sulfuric acid is the

(1) hydroxide ion (2) hydronium ion (3) sulfite ion (4) sulfate ion

9. Which process uses a volume of solution of known concentration to determine the concentration of another

solution?

(1) distillation (2) substitution (3) titration (4) double replacement

10. Which pH change represents a hundredfold increase in the concentration of H3O+1

?

(1) pH 5 to pH 7 (2) pH 13 to pH 14 (3) pH 3 to pH 1 (4) pH 4 to pH 3

11. Which compound is an Arrhenius base?

(1) CH3OH (2) CO2 (3) LiOH (4) NO2

12. Which statement correctly describes a solution with a pH of 9?

(1) It has a higher concentration of H3O+ than OH

– and causes litmus to turn blue.

(2) It has a higher concentration of OH– than H3O

+ and causes litmus to turn blue.

(3) It has a higher concentration of H3O+ than OH

– and causes methyl orange to turn yellow.

(4) It has a higher concentration of OH– than H3O

+ and causes methyl orange to turn red.

13. Which of these 1 M solutions will have the highest pH?

(1) NaOH (2) CH3OH (3) HCl (4) NaCl

14. Which species can conduct an electric current?

(1) NaOH(s) (2) NaCl (s) (3) H2O(l) (4) HCl(aq)

15. A compound whose water solution conducts electricity and turns phenolphthalein pink is

(1) HCl (2) HNO3 (3) NaOH (4) LiCl

51

Use this info for #16 – 18:

Indigestion may be caused by excess stomach acid (hydrochloric acid). Some products used to treat indigestion

contain magnesium hydroxide. The magnesium hydroxide neutralizes some of the stomach acid. The amount of

acid that can be neutralized by three different brands of antacids is shown in the data table below.

16. Based on Reference Table F, describe the solubility of magnesium hydroxide in water.

17. Show a correct numerical setup for calculating the milliliters of HCl(aq) neutralized per gram of antacid tablet

for each brand of antacid.

18. Which antacid brand neutralizes the most acid per gram of antacid tablet?

19. Given the following solutions: Solution A: pH of 10

Solution B: pH of 7

Solution C: pH of 5

Which list has the solutions placed in order of increasing H+ concentration?

(1) A, B, C (2) B, A, C (3) C, A, B (4) C, B, A

20. Which of these pH numbers indicates the highest level of acidity?

(1) 5 (2) 8 (3) 10 (4) 12

21. According to the Arrhenius theory, when a base dissolves in water it produces

(1) CO32–

as the only negative ion in solution (3) NH4+1

as the only positive ion in solution

(2) OH-1

as the only negative ion in solution (4) H+1

as the only positive ion in solution

22. Which solution when mixed with a drop of bromthymol blue will cause the indicator to change from blue to

yellow?

(1) 0.1 M HCl (2) 0.1 M NH3 (3) 0.1 M CH3OH (4) 0.1 M NaOH

52

Use the following info for questions #23 – 26:

A titration setup was used to determine the unknown molar concentration of a solution of NaOH.

A 1.2 M HCl solution was used as the titration standard. The following data were collected.

23. Calculate the volume of NaOH solution used to neutralize 10.0 mL of the standard HCl solution in trial 3.

Show your work.

24. According to Reference Table M, what indicator would be most appropriate in determining the end point of

this titration? Give one reason for choosing this indicator.

25. Calculate the molarity of the unknown NaOH solution using data from Trial 3. Your answer must include the

correct number of significant figures and correct units.

26. Explain why it is better to use the average data from multiple trials rather than the data from a single trial to

calculate the results of the titration.

Use this info for Questions #27 & 28:

Calcium hydroxide is commonly known as agricultural lime and is used to adjust the soil pH. Before the lime was

added to a field, the soil pH was 5. After the lime was added, the soil underwent a 100-fold decrease in

hydronium ion concentration.

27. What is the new pH of the soil in the field?

28. According to Reference Table F, calcium hydroxide is soluble in water. Identify another hydroxide

compound that contains a Group 2 element and is also soluble in water.

r-h regents chemistry - wikispacesadnychemistry.wikispaces.com/file/view/regents... · r-h regents...

Documents