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Unit 9: Acids, Bases, & Salts

Unit Vocabulary:

Amphoteric Arrhenius acid Arrhenius base Bronsted-Lowry acid Bronsted-Lowry base Electrolyte

hydronium ion hydroxide ion indicator (acid/base) neutralization pH scale titration

Unit Objectives:

Compare and contrast properties of acids, bases, and salts Compare the Arrhenius and Bronsted-Lowry theories of acids and bases Explain and give examples of neutralization reactions Using the titration equation, determine the molarity of an unknown

solution Understand how pH works Using Table M, determine the pH of a given solution

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Characteristic Properties of Acids:

__________ acids have a __________ taste Ex: citric acid (fruit), acetic acid (vinegar), carbonic acid (soda),

boric acid used as eye-washing solution _______________ acids ______ skin & ___________ in clothing Aqueous solutions of acids are __________________ (substances

that conduct electric current when dissolved in water) ________ concentration of ____ = ______________________

________ acids = ________ conductors ________ acids = ________ conductors

Acids react with ________ to form __________ solutions

________________________________ reaction Called a __________________ reaction _______ + _______ _______ + _______

Ex: __HCl(aq) + __NaOH(aq) → __ _______ + __ _______ Acids react with certain ________ to produce _______________

________________________ reaction (Table J) _______ + _______ _______ + __________________

Ex: __HCl(aq) + __Na(s) → __ _______ + __ _______

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Acids cause acid-base _______________ to _________________ Ex: litmus paper turns red, phenolphthalein turns from pink to

colorless Acids have ____________ < ___ (fall on _______ end of pH SCALE)

General formula = ___ or ___ (Where X = ________ such as ___ )

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ACIDIC NEUTRAL BASIC

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Characteristic Properties of Bases:

_________ bases have a _________ taste Ex: antacids, soaps, ammonia-based cleaning products

Bases have a _____________ or ___________ feel

_______________ bases ______ skin & ___________ in clothing Aqueous solutions of bases are _________________ (substances

that conduct electric current when dissolved in water) __________ concentration of _____ = ___________________

________ bases = _______ conductors ________ bases = _______ conductors

________ react with ________ to form __________ solutions

___________________________ reaction Called a __________________ reaction _______ + _______ _______ + _______

Ex: __HBr(aq) + __Ca(OH)2(aq) → __ _______ + __ _______ Bases cause acid-base _______________ to __________________

Ex: litmus paper turns blue, phenolphthalein turns from colorless to pink

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Bases have ___________ < ___ (fall on _______ end of pH SCALE)

General formula = _____ (Where X = __________ such as ___ )

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ACIDIC NEUTRAL BASIC

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Characteristic Properties of Salts:

Defined as __________________________ that have ________ ___________________________ and ____________________ ___________________; composed of a positively charged metal or polyatomic ion AND a negatively charged nonmetal or polyatomic ion (with the exception of –OH- which would then make it a base)

Examples of salts ______, ______, ______, ______ Salts are FORMED FROM _______________________________

and are _____________

Exception to the rule: NH4Cl is the salt of a weak acid

Electrolyte = A substance that _______________________ to form _______________ and therefore ___________________________

________, ________, & ________

ARE ALL ________________ (in _____________)

(http://cwx.prenhall.com/petrucci/medialib/media_portfolio/text_images/015_ELECTANDNON.MOV)

acid + base ______ + water

NH4Cl → _____ + Cl- NH4

+ is a weak acid, which means it produces H+ in solution

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Rules for Naming Acids: Binary Acids acids that START WITH H and are attached to a NONMETAL; ________________________ in acid’s formula

1st word in name Begin with _________- & follow it up immediately with the name of the other element while replacing the ending with -____ 2nd word in name add the word ________ as the second (last) word in the name

Ex: HCl

Ex: HI

Ex: HBr

Ternary Acids acids that START WITH H & are attached to a POLYATOMIC ION; ________________________ in the compound formula—USE TABLE E!

1st word in name: There is NO “HYDRO” in front! Same rules as the binary acids, except the suffixes –____ and -____ are replaced by –____ and –____ (respectively)

So: If the polyatomic ion ends in -ATE it gets replaced by –IC (I ate in the café and went ic!)

If the polyatomic ion ends in -ITE it gets replaced by –OUS

2nd word in name: Add the word acid as the second word in the name

Ex: HNO3 Ex: HNO2

Ex: HC2H3O2

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**There are a couple compounds that have SLIGHT EXCEPTIONS to the rules outlined above. Sometimes you must just go with what “rolls off the tongue” more smoothly!

Ex: H2SO3 Ex: H2SO4

Rules for Naming Bases: *much easier than Naming Acids!

1) Name the _________ in the formula “_________.” This will always be the + ion and will either be a metal (ex: Na) or a polyatomic ion (ex: NH4)

2) Name the -OH ON THE END AS __________ (separate second word in the name) – Table E says that OH is called “hydroxide”

3) NOTE: it does not matter how many you have of each when it comes to the positive or negative ion (see second example below). Don’t ever use prefixes!

Ex: LiOH

Ex: Mg(OH)2 Ex: NH4OH

Practice Naming:

Acid Name Acid Formula Anion name/Symbol Hydrobromic acid

H2S

Carbonic acid

HClO2

Base Name Formula Ca(OH)2

Sodium hydroxide

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Acid/Base Theories An Arrhenius Acid is defined as a substance whose water (aqueous) solution contains or yields ____________ IONS (___ IONS) as the ___________________________ in solution

Examples: HCl H+

(aq) + Cl-(aq)

H2SO4 H+ + H+ + SO4-2

______ acids → ____________________________

GENERAL RULE FOR ACIDS: HYDROGEN (H) is the FIRST ION

seen in the formula (H is always the POSITIVE ION)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ** NOT ALL SUBSTANCES THAT CONTAIN HYDROGEN ARE ACIDS. Below is a list of covalent hydrogen compounds that do not dissociate to yield H+ ions.

Non-Examples of Acids: _______ = water (neutral & amphoteric) _______ = methane (natural gas) _______ = glucose (sugar) _______ = hydrogen peroxide _______ = ammonia (a weak BASE!!!)

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THE HYDRONIUM ION: http://www.chemistry.uoguelph.ca/educmat/chm19104/chemtoons/chemtoons2.htm

Let’s recall what happens when a hydrogen atom becomes an ion:

(Lose e-) H H+ + e-

Thus, a ______________________ is essentially a _________. When in water, this _________ is naturally ___________ to the unshared electrons and slight negative charge of the oxygen in the water. It is believed that the hydrogen ion cannot exist as an isolated particle so what forms is called a _____________________ (________).

According to the Arrhenius theory, the properties of acids are functions of these hydronium (hydrogen) ions. So, because of this, we say that H+ = H3O+

DIFFERENT TYPES OF ARRHENIUS ACIDS:

__________ acids (1 H+) acids that ionize in __________; acids that produce ______________ in solution

Ex: HCl ___ + ___

__________ acids (2 H+) acids that ionize in __________; acids that produce ______________ in solution

Ex: H2SO4 ___ + ________

HSO4- ___ + ________

__________ acids (3 H+) acids that ionize in __________; acids

that produce ______________ in solution Ex: H3PO4 ___ + ________

H2PO4- ___ + ________

HPO42- ___ + ________

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An Arrhenius Base is defined as a substance whose water (aqueous) solution contains or yields/produces ____ (_______________ IONS) as the ________________________________ when dissolved in water.

Examples: ___________, ____________ GENERAL RULE FOR BASES: contains –____ at the end of the formula

**One Exception to Rule: NH3 = ________________ _______________ Bases produce 1 –OH in aqueous soln (single step).

Example: KOH _____ + _____

_______________ Bases produce 2 –OH in aqueous soln (single step).

Example: Ca(OH)2 _____ + _____

_______________ Bases produce 3 –OH in aqueous soln (single step).

Example: Al(OH)3 _____ + _____ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ **Not all compounds that contain –OH are bases. For example, __________ and _________________ are _______________. Below is a list of compounds that contain –OH but do not dissociate to yield OH- ions.

Non-Examples of Bases: ______ = water (neutral & amphoteric) _______ = methanol (an alcohol) __________ = methanoic acid (an organic acid)

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Alternate Acid-Base Theory (AKA ________________ Theory)

This theory explains the behavior of _____________ & ______________

Definitions of the Theory:

BRONSTED-LOWRY _______ are the _______________________ ___________________________________________________

Circle the B-L Acid below: BRONSTED-LOWRY _______ are the _______________________

___________________________________________________ Circle the B-L Base below:

Bronsted-Lowry Conjugate Pairs:

We will use TWO BRACKETS connecting one side of the reaction to the other to represent the ACID-BASE CONJUGATE PAIRS (each member within the pair DIFFERS from the other BY MERELY ONE HYDROGEN)

HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq)

Notice: The acid always has one more H than the base!

KEY A = Acid B = Base CA = Conjugate Acid CB = Conjugate Base

H2O + + OH -

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Use brackets and the key from the example on the previous page to indicate the conjugate pairs in the equations below.

Practice Problem 1: NH3 + HOH NH4

+ + OH-

Practice Problem 2: HCl + HOH Cl- + H3O+ Practice Problem 3: HI + HOH I- + H3O+

Practice Problem 4:

HNO3 + H2O H3O+ + NO3

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Amphoteric/Amphiprotic = A substance that can _______________

_______________ (can behave as a proton donor or proton acceptor) Example: WATER is amphoteric (see below)

H2O + H2O H3O+ + OH-

*Amphoteric substances must have at least one ______________ in their formula

Ex: Which of the following substances is amphoteric?

a.) H2SO3

b.) HBr

c.) HSO3-

d.) Br-

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The pH Scale - The Power of Hydrogen:

pH = direct measurement of _______________________ in a solution The pH scale is designed to measure ___________ or ____________ an aqueous solution is. The concentration of hydronium and hydroxide ions in a solution will determine whether a solution is acidic or basic. The pH scale ranges from ___ TO ___ (ACIDIC neutral BASIC)

In an acidic substance [H+] > [OH-] (brackets indicate concentration) In a basic substance [H+] < [OH-] In a neutral substance [H+] = [OH-] Example: H2O

The pH scale is LOGARITHMIC (based on exponents of the number 10)

1. log (10) = ___

2. log (100) = ___

3. log (1) = ___

4. log (.01) = ___

The pH of a solution is the negative log of the [H+]:

pH = -log[H+]

1. pH of 1.0 M HClO4 = -log (1.0) = ________

2. pH of .5 M H2SO4 = -log (.5) = ________

3. pH of .01 M HBr = -log (.01) = ________

4. pH of 12 M HCl = -log (12) = ________

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ACIDIC NEUTRAL BASIC

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For basic solutions, find the pOH using the negative log of the [OH-], then subtract that value from 14 to get the pH:

pOH = -log[OH-]

pH = 14 – pOH

1. pH of 1.0 M NaOH = 14-(-log (1.0)) = ________

2. pH of .5 M Ca(OH)2 = 14-(-log (0.1)) = ________

3. pH of .01 M LiOH = 14-(-log (0.01)) = ________

4. pH of 6.0 M KOH = 14-(-log (6.0)) = ________

Each change of a SINGLE pH UNIT signifies A TENFOLD CHANGE IN [H+] CONCENTRATION

Ex: going from a ph of 4 to a pH of 5

Becoming ______ basic; [OH-] __________ by _______

Becoming ______ acidic; [H+] __________ by _______

Ex: going from a pH of 13 to a pH of 10

Becoming ______ acidic; [H+] __________ by _______

Becoming ______ basic; [OH-] __________ by _______

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(Where some common substances fall on the pH scale)

STRONG acids and bases ionize 100%: http://www.chemistry.uoguelph.ca/educmat/chm19104/chemtoons/chemtoons3.htm

Strong base (sodium hydroxide): NaOH (s) _____ + _____ (100% ionization)

Strong acid (hydrochloric acid): HCl(g) _____ + _____

(100% ionization) WEAK acids and bases have < 100% ionization (partial ionization) http://www.chemistry.uoguelph.ca/educmat/chm19104/chemtoons/chemtoons4.htm

Strong acid (acetic acid): HC2H3O2 ______ + _________

(partial ionization) http://www.mhhe.com/physsci/chemistry/chang7/esp/folder_structure/ac/m2/s2/index.htm

Weak Base (ammonia): NH3 + H2O ______ + ______ (partial ionization)

Strong Acids Strong Bases

HCl LiOH

HBr NaOH

HI KOH

H2SO4 RbOH

HNO3 CsOH

HClO4 Ba(OH)2

Sr(OH)2

Ca(OH)2

*Ammonia and the –OH in water battle for hydrogen. Roughly 1/10,000 times, ammonia wins, generating a SLIGHT excess of OH – ions, making the solution BASIC.

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Acid-Base Indicators (Table M): http://en.wikipedia.org/wiki/Phenolphthalein

Indicator = substance (weak acid) that _________________ as a result of a ________________; indicators are chosen based on their __________ for ___________________

Ex: Phenolphthalein COLORLESS up until a pH of 8, LIGHT PINK from 8 to 9, and PINK at a pH greater than 9

Ex: Methyl Orange turns RED in a solution with a pH of less than 3.1, ORANGE between 3.1 and 4.4, and YELLOW in a solution with a pH greater than 4.4

*Litmus listed is liquid litmus (similar to paper litmus) ** Within the “Approximate pH Range for Color Change” a MIXTURE

OR BLENDING of the two colors listed occurs. This range is therefore also called the INTERMEDIATE COLOR REGION.

1. bromthymol blue at a pH of 6.4 ____________________ 2. bromcresol green at a pH of 5.0 ____________________ 3. phenolphthalein at a pH of 9.2 ____________________ 4. methyl orange at a pH of 3.9 ____________________

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Using reference table M, complete the chart below.

Indicator pH of sample Color indicator will turn

methyl orange 6.0

bromothymol blue 2.0

phenolphthalein 7.0

Litmus 6.8

bromocresol green 3.0

thymol blue 7.0

methyl orange 2.2

bromothymol blue 8.2

phenolphthalein 10

Litmus 3.2

bromocresol green 6.2

thymol blue 10

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Neutralization Reactions: http://www.marymount.k12.ny.us/marynet/06stwbwrk/06hchem/mgFlash/mgreaction.html

Neutral = neither acidic nor basic; [H+] = [OH-] Neutralization occurs when an Arrhenius acid and an Arrhenius base react to form __________ and a ___________ Example: Antacid for upset stomach neutralizes the acid in stomach

and makes a neutral salt to provide relief General reaction for neutralization reactions:

(1) The ___ from the acid and the ___ from the base combine to form water.

(2) The ________ from the acid and the ________ from the base combine to produce a salt.

*Neutralization rxns are always _____________________ reactions! **Remember, just like any compound, the (+) and (-) charges must be

balanced. Use the Criss Cross Rule to figure out the correct formula for the salt – water is always the formula H2O!

Net ionic equation for neutralization reactions (after spectator ions are crossed out):

H+(aq) + OH-(aq) H2O(l)

ACID + BASE _______ + _______

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Complete the following reactions. Make sure they are balanced!

1. HBr + KOH __________ + __________ 2. NaOH + HC2H3O2 __________ + __________

3. KOH + H3PO4 __________ + __________

4. 2HNO3 + Ca(OH)2 __________ + __________

Do we always get a completely neutral solution?

Combination Product (Acidic/Basic/Nuetral)

Endpoint pH (<7, 7, >7)

Strong acid + Strong Base

Strong acid + Weak Base

Weak acid + Strong Base

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(Acid-Base) Titration:

Titrations are used to CALCULATE THE CONCENTRATION (MOLARITY) OF AN UNKNOWN SOLUTION

Acid of unkown molarity is reacted with a carefully measured amount of a base of known molarity to the point of _____________________ (or vice versa)

In all neutralization reactions there must be a _____________ between the ______________________ and the ______________________ So, in a titration, when:

_______ = _______ or

______________________ = ______________________

that means you’ve reached the _____________________ of the reaction; this is when the titration is complete. The ______________ of a titration is the pH at which the solution changes color permanently.

What does a Titration look like?

http://auth.mhhe.com/physsci/chemistry/animations/chang_7e_esp/crm3s5_5.swf

Titration formula (Table T): MA VA = MB VB Where: MA = molarity of acid (H+)

VA = volume of acid MB = molarity of base (OH-) VB = volume of base

Use this formula when you are dealing with a

titration or neutralization word problem Make sure that all units are in agreement

when plugging into formula (so they cancel out and you get the right answer!)

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Sample Problem 1: What is the concentration of a solution of HI if 0.3 L is neutralized by 0.6 L of 0.2 M solution of KOH? Sample Problem 2: What is the concentration of a hydrochloric acid solution if 50.0 mL of a 0.250 M KOH solution are needed to neutralize 20.0 mL of the HCl solution of unknown concentration? Sample Problem 3: A particular acid has an H+ concentration of 0.1 M and a volume of 100 mL. What volume of a base with a 0.5 M [OH-] will be required to neutralize the reaction? **Sample Problem 4: You have 50 mL of 1.0 M H2SO4(aq). What volume of 0.5 M NaOH would be required to neutralize the acid? Remember Diprotic Acids yield 2 H+ ions in solution!

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Reactions of Metals with Acids:

According to Table J in your Reference Tables, any __________ LOCATED ______________________________________ to produce _____________________ Example: Which metal, Mg or Cu will react with HCl? ________

General Rxn:

Ex: Zn + 2HCl ____ + _____ Of the four types of reactions that we have learned, this is a ____________ _______________ reaction; notice how __________ is produced! Ex: ___, ___, & ___ do not react with acids because they are located ___________ on Table J (notice these are metals used for JEWELRY!)

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Reactions of Metals with Water: GROUP I METALS:

All Group I metals react vigorously with “cold” water

GROUP II METALS:

Berryllium has no reaction with “cold” water or steam, even at red heat

Magnesium has only a slight reaction with “cold” water, and magnesium burns in steam to produce white magnesium oxide and hydrogen gas:

Mg(s) + H2O(g) → _____(s) + _____ (g)

Calcium, Strontium, and Barium all react with “cold” water with increasing vigor to produce metal hydroxide and hydrogen gas:

X(s) + 2H2O(g) → _____ (aq) + _____ (g)

Summary of the trend for Group II Metals: the Group II Metals become more reactive with water as you go DOWN the group