quiz 2

Quiz 2

Due: 11:59pm on Wednesday, September 19, 2012

Note: You will receive no credit for late submissions. To learn more, read your instructor's Grading Policy

Question 1

Give the name or chemical formula, as appropriate, for each of the following acids.

Part A

,

ANSWER:

Correct

Part B

,

ANSWER:

Correct

Part C

,

ANSWER:

Correct

Part D

hypochlorous acid,

Express your answer as a chemical formula.

ANSWER:

Correct

Part E

iodic acid,

bromic acid

hydrobromic acid

phosphoric acid


ANSWER:

Correct

Part F

sulfurous acid.


ANSWER:

Correct

Question 2

Learning Goal:

To learn to write the systematic name of ionic compounds given the chemical formula and to write the chemical formula given the systematic name.

Ionic bonds form when one atom completely transfers one or more electrons to another atom, resulting in the formation of ions. Positively charged ions(cations) are strongly attracted to negatively charged ions (anions) by electrical forces. All chemical compounds can be named systematically by following aseries of rules. Binary ionic compounds are named by identifying first the positive ion and then the negative ion. Naming compounds with polyatomic ionsinvolves memorizing the names and formulas of the most common ones.

Part A

Give the systematic name for the compound .

Hint 1. How to approach the problem

When naming ionic compounds, the cation is identified first and the anion is identified second.

Hint 2. Name the anion

What is the name of the polyatomic anion ?

Hint 1. Naming polyatomic ions

It is generally necessary to memorize the names of polyatomic ions such as (hydroxide), (ammonium), or (sulfite).

However, there are a few guidelines:

The names of most polyatomic ions end in ite or ate.Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, sulfur cancombine with three or four oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer

oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name istaken from the name of the element that combines with the oxygen atoms. Thus, is the sulfite ion and is the

sulfate ion.

Nitrogen forms two oxoanions, and .

ANSWER:

ANSWER:

CorrectAluminum is a metal that has only one oxidation state. Therefore it is not necessary to write III in parentheses in the systematic name. Only thosemetals with more than one oxidation state must have its state written in the name.

Part B

Give the systematic name for the compound .


When naming ionic compounds, the cation is identified first and the anion is identified second. If the metal has more than one oxidation state,identify the oxidation state using a Roman numeral in parentheses immediately after the metal name.

Hint 2. Name the anion

What is the systematic name of the anion ?

Hint 1. Naming polyatomic ions

It is generally necessary to memorize the names of polyatomic ions such as (hydroxide), (ammonium), or (sulfite).

However, there are a few guidelines:

The names of most polyatomic ions end in ite or ate.Oxoanions are ions in which a given element combines with different numbers of oxygen atoms. For example, nitrogen cancombine with two or three oxygen atoms, forming or . When there are only two oxoanions, the ion with fewer

oxygen atoms has the ending ite, and the ion with more oxygen atoms has the ending ate. The first part of the name istaken from the name of the element that combines with the oxygen atoms. Thus, is the nitrite ion and is the

nitrate ion.

Sulfur forms two oxoanions, and .

ANSWER:

Hint 3. Determine the oxidation number

What is the charge of the iron cation in this ionic compound.

ANSWER:

nitrate

aluminium nitrate

sulfate

ANSWER:

CorrectAlthough it seems like a small difference, iron(II) and iron(III) behave much differently chemically. They even form different-colored compoundsbecause of the number of electrons they have to bond. Therefore it is very important to specify which oxidation state is being used.

Part C

Write the formula for the compound magnesium oxide.



Use the periodic table to determine the charge for each ion. Because this is a neutral ionic compound, the positive charges must equal thenegative charges. Reduce the subscript on each ion to its lowest whole number ratio.

Hint 2. Determine the charge of the anion

What is the charge of the oxide ion?

Hint 1. Group 16 elements

Oxygen is in group 16 on the periodic table. This group is also known as group 6A using the U.S. system. Main group nonmetals usuallyform anions whose charge is equal to the U.S. system group number minus eight.

ANSWER:

Hint 3. Determine the charge of the cation

What is the charge of the magnesium ion?

3

2

0

+1

+2

+3

iron(III) sulfate

4

3

2

1

0

+1

+2

+3

Hint 1. Alkaline earth metals

By consulting the periodic table, we can determine that magnesium is an alkaline earth metal. Main group metals usually form cationswhose charge is equal to the group number.

ANSWER:

ANSWER:

CorrectAll of the elements in group 2 form ions with a +2 charge. That is because all of these elements need to lose two electrons to gain stability. Afterlosing the electrons, there is an excess of two protons, which results in a +2 charge.

Part D

Write the formula for the compound lead(II) phosphate.



The oxidation number of the cation is given. The anion is polyatomic, so you will have to look up its formula and charge. Because this is aneutral ionic compound, the positive charges must equal the negative charges. Reduce the subscript on each ion to its lowest whole numberratio.

Hint 2. Determine the formula for the phosphate ion

What is the formula for the phosphate anion?


The phosphate ion is an oxoanion composed of two elements: phosphorus and oxygen. Consider that a similar ion, the phosphite ion,has the formula .

ANSWER:

2

1

0

+1

+2

+3

+4

Hint 3. Balance the charges

Lead(II) has a charge of +2 and phosphate has a charge of 3. Therefore, the lead(II) phosphate formula must have _____ lead(II) ions and

_____ phosphate ions for the charges to balance.

Hint 1. Charges in neutral compounds

Because this is a neutral ionic compound, the total number of positive charges [from the lead(II) ion] must equal the total number ofnegative charges (from the phosphate ion).The lead(II) ion has a +2 charge and the phosphate ion has a 3 charge. Therefore, if there were only one lead(II) ion and one

phosphate ion, the overall charge would be 1, because . To have an overall charge of 0, this compound will have

more than one of each ion. That is, both ionsiron(II) and chloridewill have subscripts.

ANSWER:

ANSWER:

CorrectLead, like iron, has more than one oxidation state, so it is necessary to put the oxidation state of the metal in brackets. Elements in group 1 and 2only have one oxidation state and so there is no need for Roman numerals in their systematic name.

Question 3

The coefficients in a balanced chemical equation provide the mole-to-mole stoichiometry among the reactants and products. The molar mass (in )

can be used as the conversion factor between moles and the mass of a substance. Thus, the balanced equation and molar masses can be used inconjunction with one another to calculate the masses involved in a reaction.

Complete combustion of methane

When methane ( ) burns, it reacts with oxygen gas to produce carbon dioxide and water. The unbalanced equation for this reaction is

This type of reaction is referred to as a complete combustion reaction.

Part A

one / one

one / two

one / three

two / one

two / three

three / two

What coefficients are needed to balance the equation for the complete combustion of methane? Enter the coefficients in the order , , , and

, respectively.

Express your answer as four integers, separated by commas (e.g., 1,2,3,4).


First, balance the carbon atoms. Second, balance the hydrogen atoms. Third, balance the oxygen atoms. Finally, double check that all atomsare balanced.

ANSWER:

CorrectThe balanced chemical equation is therefore:

Part B

What mass of carbon dioxide is produced from the complete combustion of 4.70!10"3 of methane?

Express your answer numerically in grams.


First, convert the mass of methane to moles. Then, use the balanced equation to convert moles of methane to moles of carbon dioxide. Finally,convert moles of carbon dioxide to grams.

Hint 2. Determine the number of moles of methane

How many moles of methane are in 4.70!10"3 ?

Express your answer numerically in moles.

Hint 1. Determine the molar mass of methane

What is the molar mass of methane, ? Use the periodic table as needed.

Express your answer numerically in grams per mole.

ANSWER:

ANSWER:

Hint 3. Find the number of moles of carbon dioxide

How many moles of are produced from the given amount of ?


1,2,1,2

16.0

2.93!10"4

Hint 1. Determine the stoichiometry between methane and carbon dioxide

Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of carbon dioxide?

ANSWER:

ANSWER:

Hint 4. Determine the molar mass of carbon dioxide

What is the molar mass of carbon dioxide? Use the periodic table as needed.

Express your numerically in grams per mole.

ANSWER:

ANSWER:

Correct

Part C

What mass of water is produced from the complete combustion of 4.70!10"3 of methane?



First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of water. Finally,convert moles of water to grams of water.

Hint 2. Find the number of moles of water

How many moles of are produced from the given amount of ?



First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine the

2.93!10"4

44.0

1.29!10"2

mole ratio of water to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convertfrom moles of methane to moles of water.

Hint 2. Determine the stoichiometry between methane and water

Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of water?

ANSWER:

CorrectUse the conversion formula

to convert the given number of moles of methane to the corresponding number of moles of water.

ANSWER:

Answer Requested

Hint 3. Determine the molar mass of water

What is the molar mass of water? Use the periodic table as needed.


ANSWER:

Answer RequestedThe molar mass in the form

can be used to convert moles to grams.

ANSWER:

5.86!10"4

18.0

1.06!10"2

Answer Requested

Part D

What mass of oxygen is needed for the complete combustion of 4.70!10"3 of methane?



First, convert the mass of methane to moles. Second, use the balanced equation to convert moles of methane to moles of oxygen. Finally,convert moles of oxygen to grams of oxygen.

Hint 2. Convert to moles of oxygen

How many moles of are needed to react with the given amount of ?



First, determine the number of moles of methane that react (you should have already figured this out in Part B). Second, determine themole ratio of oxygen to methane given in the balanced equation (which you figured out in Part A). Finally, use the mole ratio to convertfrom moles of methane to moles of oxygen.

Hint 2. Determine the stoichiometry between methane and oxygen

Which of the following would be the correct stoichiometric ratio to convert from moles of methane to moles of oxygen?

ANSWER:

ANSWER:

Hint 3. Determine the molar mass of oxygen

What is the molar mass of ? Use the periodic table as needed.

Express your answer in grams per mole.

ANSWER:

5.86!10"4

32.0

ANSWER:

Correct

Question 4

A phase diagram is a convenient means of representing the temperature and pressure dependence of a pure substance in a closed system. The typicalphase diagram indicates which phase (solid, liquid, or gas) is stable at a given temperature and pressure. Boundaries separate these phase regions. Whena boundary line is crossed owing to changes in temperature and/or pressure a phase change occurs.

Part A

Identify each of the labeled points (indicated with letters) or changes (indicated with two letters separated by an arrow) shown on the phase diagram.

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.

Hint 1. Identify the regions of the phase diagram

Identify which physical state is shown by each of the colored regions labeled with the letters X, Y, and Z on the phase diagram.

Drag each item to the appropriate bin.

Hint 1. Relation of pressure and temperature to phase

High pressure and low temperatures tend to favor the condensed phases whereas low pressure and high temperatures tend to favor thegas state. Use the axes on the diagrams to help identify these conditions.

ANSWER:

1.88!10"2

Hint 2. Define the specific characteristics of the phase diagram

Complete the following sentences related to phase diagrams.

Match the words in the left-hand column with the appropriate blank in the sentences in the right-hand column.

ANSWER:

ANSWER:

Correct

Part B

The phase diagram for an organic compound is shown.

What is the normal boiling point of this compound?

Express your answer numerically in degrees Celsius.

Hint 1. Definition of normal boiling point

The normal boiling of a substance is the temperature required to establish liquid-vapor equilibrium at standard pressure. On a phase diagram,this point occurs where the liquid-vapor line crosses standard pressure.

Hint 2. Identify the value of standard pressure

What is the value of standard pressure?

Express your answer numerically in atmospheres.

ANSWER:

standard pressure = 1.00

ANSWER:

Correct

Question 5

The fluorocarbon compound has a normal boiling point of 47.6 . The specific heats of and are 0.91 and 0.67

, respectively. The heat of vaporization for the compound is 27.49 .

Part A

Calculate the heat required to convert 73.5 of from a liquid at 14.60 to a gas at 76.40 .

Express your answer using one decimal place.

ANSWER:

Correct

Question 6

Chemists often use molarity , in , to measure the concentration of solutions. Molarity is a common unit of concentration because the volume

of a liquid is very easy to measure. However, the drawback of using molarity is that volume is a temperature-dependent quantity. As temperature changes,density changes, which affects volume. Volume markings for most laboratory glassware are calibrated for room temperature, about 20 .

Fortunately, there are several other ways of expressing concentration that do not involve volume and are therefore temperature independent.

A mass of 0.630 of is dissolved in 525 of water.

Part A

Calculate the molality of the salt solution.

Hint 1. Formula for molality

By definition

Hint 2. Solute vs. solvent

In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, thesolvent is the substance present in the greatest amount.

Hint 3. Determine the number of kilograms of water

Convert the mass of water to kilograms.

ANSWER:

normal boiling point = 150

= 14.4

ANSWER:

Correct

Part B

Calculate the mole fraction of salt in this solution.

Hint 1. Formula for mole fraction

By definition

Hint 2. Solute vs. solvent

In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, thesolvent is the substance present in the greatest amount.

Hint 3. Calculate the number of moles of NaCl

How many moles of NaCl are in 0.630 ?

Hint 1. Find the molar mass of NaCl

What is the molar mass of ?


ANSWER:

ANSWER:

Hint 4. Calculate the number of moles of water

How many moles of water are in 525 ?

Hint 1. Find the molecular weight of water

What is the molecular weight of water?


Hint 1. Formula for water

0.525

2.05!10"2

58.5

1.08!10"2

The chemical formula for water is .

ANSWER:

ANSWER:

ANSWER:

Correct

Part C

Calculate the concentration of the salt solution in percent by mass.

Hint 1. Formula for percent by mass

By definition

Hint 2. Solute vs. solvent vs. solution

In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, thesolvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.

Hint 3. Find the mass of the solution

What is the mass of this solution?

Express your answer five significant figures.

ANSWER:

ANSWER:

18.0

29.2

= 3.70!10"4

525.63 g

0.120 %

CorrectThe total mass of the solution in this case is 525.63 , which makes the percent by mass come to 0.11985617%. However, when rounded to thecorrect number of significant figures, the answer becomes 0.120%.

Quite often, the mass of the solute is so small compared to the mass of the solution that

Part D

Calculate the concentration of the salt solution in parts per million

Hint 1. Formula for ppm

By definition

Hint 2. Solute vs. solvent vs. solution

In a solution formed by dissolving a solid in a liquid, the solid is called the solute and the liquid is called the solvent. In any type of solution, thesolvent is the substance present in the greatest amount. The word "solution" refers to solvent plus solute.

ANSWER:

CorrectThe word percent means "per 100" (think of century). Therefore, an alternate name for percent by mass could be "parts per hundred." This shouldhelp you see the similarity between percent and parts per million:

Question 7

Indicate the type of solute-solvent interaction that should be most important in each of the following solutions.

Part A

in benzene

ANSWER:

Correct

1200

dispersion forces

dipole-dipole forces

ion-dipole forces

hydrogen bonding

Part B

methanol in water

ANSWER:

Correct

Part C

in water

ANSWER:

Correct

Part D

in acetonitrile

ANSWER:

Correct

Question 8

dispersion forces


ion-dipole forces

hydrogen bonding

dispersion forces


ion-dipole forces

hydrogen bonding

dispersion forces


ion-dipole forces

hydrogen bonding

By referring to the figure , determine whether the addition of 40.0 of each of the following ionicsolids to 100 of water at 40 will lead to a saturated solution.

Part A

ANSWER:

Correct

Part B

ANSWER:

Correct

Part C

ANSWER:

Correct

Part D

saturated solution

unsaturated solution

saturated solution


saturated solution


ANSWER:

Correct

Question 9

Ascorbic acid (vitamin C, ) is a water-soluble vitamin. A solution containing 80.5 of ascorbic acid dissolved in 230 of water has a density of 1.22

at 55 .

Part A

Calculate the mass percentage.

ANSWER:

Correct

Part B

Calculate the mole fraction.

ANSWER:

Correct

Part C

Calculate the molality.

ANSWER:

Correct

Part D

Calculate the molarity of ascorbic acid in this solution.

ANSWER:

saturated solution


25.9 %

3.46!10"2

1.99

= 1.80

Correct

Question 10

Calculate the number of moles of solute present in each of the following solutions.

Part A

270 of 1.50

ANSWER:

Correct

Part B

55.0 of an aqueous solution that is 1.50

ANSWER:

All attempts used; correct answer displayed

Part C

80.0 of an aqueous solution that is 1.70% sucrose ( ) by mass

ANSWER:

Correct

Question 11

Part A

Calculate the vapor pressure of water above a solution prepared by dissolving 38.0 of glycerin ( ) in 135 of water at 343 . (The vapor

pressure of water at 343 is 233.7 .)

ANSWER:

= 0.405

= 7.59!10"5

= 3.97!10"3

= 222

Correct

Part B

Calculate the mass of ethylene glycol ( ) that must be added to 1.00 of ethanol ( ) to reduce its vapor pressure by 12.0 at 35

. The vapor pressure of pure ethanol at 35 is torr.

ANSWER:

Correct

Question 12

The molar mass of a compound expresses the ratio of mass to moles:

This quantity can be determined experimentally by accurately measuring the mass of the sample and determining the corresponding number of molesbased on some property of the sample. Freezing point depression and osmotic pressure measurements are frequently used for this type of determination.In each instance, the number of moles is determined from the colligative property of the solution. For osmotic pressure measurements, the number ofmoles is calculated from the volume of the solution and the molarity. In freezing point depression measurements, the number of moles is derived from themolality of the solution.

Part A

tert-Butyl alcohol is a solvent with a of 9.10 and a freezing point of 25.5 . When 0.807 of an unknown colorless liquid was dissolved in

11.6 of tert-butyl alcohol, the solution froze at 15.3 .

Which of the following is most likely the identity of this unknown liquid?


First, calculate the freezing point depression by subtracting the two freezing points:

Next, calculate the molality, , using the equation

Next, convert the mass of solvent to kilograms and use the definition of molality,

to determine the number of moles of solute, Finally, use the mass and number of moles of solute to calculate the molar mass in grams permole.

Hint 2. Calculate the freezing point depression of the solution

What is the value of the freezing point depression, , of the solution?

Express your answer numerically in degrees Celsius.

ANSWER:

Hint 3. Determine the molality of the solution

= 184

10.2

What is the molality of the solution?

Express the concentration numerically as molality.

Hint 1. What equation to use

Based on freezing point depression and the freezing point depression constant of the solvent, the following equation can be solved formolality:

ANSWER:

Hint 4. Convert the mass of solvent to kilograms

What is the mass of the solvent in kilograms?

Express the mass numerically in kilograms.

Hint 1. Conversion factor

.

ANSWER:

Hint 5. Calculate the number of moles of solute present

Using the molality and the kilogram mass of the solvent, calculate the number of moles of solute present in the solution.


ANSWER:

Hint 6. Determine the molar mass of the solute

What is the molar mass of the solute used in this experiment?



The applicable equation to calculate molar mass is

ANSWER:

ANSWER:

1.12

1.16!10"2

1.30!10"2

62.1

Correct

Part B

A protein subunit from an enzyme is part of a research study and needs to be characterized. A total of 0.135 of this subunit was dissolved in enoughwater to produce 2.00 of solution. At 28 the osmotic pressure produced by the solution was 0.138 . What is the molar mass of the protein?

Express the molar mass numerically in grams per mole.


To calculate the molar mass, a mass and the corresponding number of moles must be known. The mass is given in the problem and thenumber of moles can be calculated from the osmotic pressure.First, convert the temperature to kelvins and solve for molarity using the equation

where . Next, convert the volume of solution to liters and use the definition of molarity,

to find the moles of solute. Finally, use the mass and number of moles of solute to calculate the molar mass.

Hint 2. Calculate the temperature in kelvins

What is the temperature when converted to the Kelvin scale?

Express the temperature in kelvins

ANSWER:

Hint 3. Calculate the molarity of the solution

Based on the osmotic pressure, what is the molarity of the protein solution?

Express the concentration numerically in molar.


Solve the following equation for the molarity:

ANSWER:

Hint 4. Convert the volume of the solution to liters

ethylene glycol (molar mass = 62.07 )

1-octanol (molar mass = 130.22 )

glycerol (molar mass = 92.09 )

2-pentanone (molar mass = 86.13 )

1-butanol (molar mass = 74.12 )

301

5.59!10"3

What is the volume of the protein solution in liters?

Express the volume numerically in liters.

Hint 1. Conversion factor

.

ANSWER:

Hint 5. Determine the number of moles of solute in the solution

How many moles of solute are present in the protein solution?



Solve the following equation for moles of solute:

ANSWER:

ANSWER:

Correct

Question 13

Part A

List the following aqueous solutions in order of decreasing boiling point. 0.120 glucose, 0.050 , 0.050 .

Rank items in order of decreasing boiling point.

ANSWER:

2.00!10"3

1.12!10"5

1.21!104

Correct

Question 14

Part A

List the following aqueous solutions in order of decreasing freezing point: 0.040 glycerin ( ), 0.020 , 0.030 phenol ( ).

Rank solutions from highest freezing point to lowest freezing point. To rank items as equivalent, overlap them.

ANSWER:

Correct

Question 15

Carbon disulfide boils at 46.30 and has a density of 1.261 .

Part A

When 0.250 of a nondissociating solute is dissolved in 400.0 of , the solution boils at 47.46 . What is the molal boiling-point-elevation

constant for ?

ANSWER:

Correct

Part B

When 5.41 of a nondissociating unknown is dissolved in 50.0 of , the solution boils at 47.08 . What is the molecular weight of the

unknown?

Express your answer using two significant figures.

ANSWER:

Correct

Score Summary:

Your score on this assignment is 90.9%.You received 13.64 out of a possible total of 15 points.

= 2.34

= 260

quiz 2

Documents

names of polyatomic

chemical formula

chemical compounds

polyatomic ions end

polyatomic anion

naming compounds

polyatomic ionsit

polyatomic ionsinvolves