Suggested Problems: p #58, 59, 65, 69, 74, 80, 85, 86, 90, 92, 93, 98, 99

Chemistry I Accelerated Study Guideline - Chapter 19

Acids, Bases and Salts

--- By the end of this unit, the skills you should be able to demonstrate

are:

1. List properties of acids and bases.

2. Define and Give Examples of Arrhenius acids and bases.

3. Classify substances as acids or bases, and identify conjugate acid- base pairs in acid-base reactions, using the Brønstead-Lowry theory.

4. Classify substances as Lewis acids or bases.

5. Complete and balance a neutralization reaction.

6. Categorize acids and bases as strong or weak using K

and K

and give examples of each.

7. Derive and Use ionization constants.

8. Define acidic and basic anhydrides. Write formulas for them.

9. Write the equation for the self-ionization of water.

10. Classify a solution as neutral, acid or base given the hydrogen-ion or hydroxide ion concentration.

11. Calculate the pH or the pOH of a solution given either the hydrogen or hydroxide ion concentration.

12. Describe the processes of hydrolysis and buffering.

13. Describe at least two methods used to measure pH.

14. State the principles and uses of indicators.

15. Explain the process of titration and perform calculations using the data from titrations.

Suggested Problems: p. 625-627 #58, 59, 65, 69, 74, 80, 85, 86, 90, 92, 93, 98, 99

Chemistry Video: Acids, Bases and Salts

1. What do acids, bases and salts form in solution?

2. Why are acids, bases and salts called electrolytes?

3. How are nerve cells like a battery?

4. Litmus turns what color in acid? Base?

5. What does an acid do in solution?

6. What is H

O

called?

7. What is the general rule about oxides and acids and bases?

8. What is a more useful definition for acids and bases using the term proton?

9. What is the Lewis theory of acids and bases?

10. What does strong and weak refer to with acids and bases?

11. Can water molecules form ions by themselves?

12. What does pH stand for?

13. What pH is Acid? Neutral? Base?

14. What is a buffer?

15. How many buffers are in human blood?

16. What is a salt?

Defining Acids and Bases

On the line next to the item, write “A” if the statement is a property of an acidic solution.

Write “B” if it is a property of a basic solution, and write “X” if it is a property of both acidic and basic solutions.

_____ 1. Often feels smooth and slippery _____ 2. has a sour taste

_____ 3. Stings in open wounds _____ 4. reacts vigorously with metals _____ 5. has a bitter taste _____ 6. turns litmus paper from blue to red _____ 7. is an electrolyte _____ 8. often looks like pure water

_____ 9. turns litmus paper from red to blue _____ 10. does not usually react with metals Answer the following questions.

11. What is the Arrhenius definition of acids and bases?

12. What is the Brønsted-Lowery definition of acids and bases?

13. Why might ammonia not be considered a base according to the Arrhenius definition while the ammonium ion is considered an acid?

14. Why is the Brønsted-Lowery definition of acids and bases considered more encompassing than the Arrhenius definition?

15. Why are Brönsted-Lowery acids and bases sometimes called proton donors and acceptors?

16. What is the Lewis definition of acids and bases?

Define each of the following:

17. Acidic Hydrogens

18. Binary Acids

19. Oxy acids

20. Carboxylic acid

21. Amines

Name the following acids and bases

____________________ 22. HNO

____________________ 23. H

PO

____________________ 24. HClO ____________________ 25. KOH ____________________ 26. H

SO

____________________ 27. H

CO

____________________ 28. HC

H

O

____________________ 29. CH

NH

Complete each of the following sentences by filling in the appropriate word or phrase from the list below.

Word List

amphoteric acid-base indicator conjugate electrolyte

hydronium ion neutralization reaction salt

30. An ionic compound that forms from an acid-base neutralization reactions is a(n) _________________.

31. A(n) __________________ is a substance that conducts electricity when dissolved in water.

32. The formula H

O

represents a(n) ______________ _______.

33. The reaction between an acid and a base is called a(n) ______________ _______________.

34. A(n) ________–________ _______________ turns one color in an acidic solution and another color in a basic solution.

35. The chloride ion (Cl

) is the __________________ base of hydrochloric acid (HCl).

Reviewing Acids and Bases

Determine whether each of the following compounds contains an acidic hydrogen.

Explain your answers 1. Nitric Acid

2. Hydrobromic acid

3. Methane

4. Hydrogen gas

For the following reactions write the formula equation, place a single arrow (-->) between the reactants and the products if the reaction goes to completion. Place a double arrow (<-->) if the reaction reaches equilibrium. For each reaction label the acid (A), the base (B), the conjugate acid (CA), and the conjugate base (CB).

5. Nitrous Acid (aq) plus water (l) Hydronium (aq) and nitrite (aq) ions

6. Hydrocyanic Acid (aq) plus water (l) Hydronium (aq) and cyanide (aq) ions

7. Nitric acid (aq) plus water hydronium ion (aq) plus nitrate ion (aq)

8. Acetic acid (aq) plus water hydronium ion (aq) plus acetate ion (aq)

9. Ammonia (aq) plus water hydroxide ion(aq) plus ammonium ion(aq)

10. hydronium ion (aq) plus hydroxide ion (aq) water plus water

Acid-Base Constant Practice Problems

1. Acetic acid is a weak acid. If the initial concentration of acetic acid is 0.200 M and the equilibrium concentration of hydronium ion is .0019 M, calculate the K

for acetic acid.

HA + H

O ---> A

+ H

O

>>>> ^K

^{= [A}

^][H

^O

^] / ^[HA]

For every one hydronium ion that forms, one conjugate base must also form so if those concentrations started equal they must end equal. Also for every hydronium ion and conjugate base that forms, one acid must have dissociated.

Therefore, the starting concentration, 0.200 M minus the amount that dissociated, 0.0019 M equals the final or equilibrium concentration of 0.1981 M

Calculating K

= (0.0019)(0.0019)/0.1981 or (0.0019)

/0.1981 = 1.82 x 10

or in sig. dig. 1.8 x 10

In most cases for weak acids the initial and the equilibrium concentrations are essentially the same.

Does subtracting the amount dissociated make a difference? Let’s compare and find out:

Calculating K

= (0.0019)

/ 0.200 = 1.805 x 10

or in sig. dig. 1.8 x 10

(no difference)

2. Ammonia is a weak base. If the initial concentration of ammonia is 0.150 M and the equilibrium

concentration of hydroxide ion is 1.6 x 10

M, calculate the K

for ammonia.

3. Butylamine is a weak base. If the initial concentration of butylamine is 0.230 M and the equilibrium concentration of hydroxide ion is 8.6 x 10

M, calculate the K

for butylamine.

4. Formic acid is a weak monoprotic acid made by ants. If the initial concentration of the formic acid is 0.10 M and the equilibrium concentration of hydronium ion is 4.2 x 10

M, calculate the K

for formic acid.

5. Isobutylamine is a weak base. If the initial concentration of isobutylamine is 0.055 M and the equilibrium concentration of hydroxide ion is 4.0 x 10

M, calculate the K

for isobutylamine.

6. Gallic acid is a weak monoprotic acid. If the initial concentration of the gallic acid is 0.280 M and the equilibrium concentration of hydronium ion is 3.3 x 10

M, calculate the K

for gallic acid.

7. Triethylamine is a weak base. If the initial concentration of triethylamine is 0.390 M and the equilibrium concentration of hydroxide ion is 4.4 x 10

M, calculate the K

for triethylamine.

8. Dipropylamine is a weak base. If the initial concentration of dipropylamine is 0.160 M and the equilibrium concentration of hydroxide ion is 0.012 M, calculate the K

for dipropylamine.

9. Uric acid is a weak monoprotic acid made by ants. If the initial concentration of the uric acid is 0.110 M and the equilibrium concentration of hydronium ion is 3.4 x 10

M, calculate the K

for uric acid.

10. Hydrocyanic acid is a weak monoprotic acid. If the initial concentration of the Hydrocyanic acid is 0.150 M and the equilibrium concentration of hydronium ion is 4.8 x 10

M, calculate the K

for cyanic acid.

11. 0.230 mol of a weak base is dissolved in water to a total volume of 1.5 L. At equilibrium the

concentration of hydroxide ion is 0.0040 M, calculate the K

for this base.

12. 0.690 mol of a weak acid is dissolved in water to a total volume of 0.75 L. At equilibrium the concentration of hydronium ion is 0.0024 M, calculate the K

for this acid.

Predict whether the final solution in each situation will be acidic, basic, neutral or if it is impossible to predict. In all cases you can assume equal concentrations of acid and base are used.

13. A strong acid reacts with a strong base 13. __________________

14. A strong acid reacts with a weak base 14. __________________

15. A weak acid reacts with a strong base 15. __________________

16. A weak acid reacts with a weak base 16. __________________

Acid-Base Hydrolysis

Hydrolysis occurs when certain salts dissolve in water to form solutions that have acidic or basic properties. A rule for predicting the properties of solutions of salts is based upon the concept of strong acids and strong bases in the Arrhenius sense. The rules are

summarized in the table below:

Salt formed from Water solution exhibits Example

Strong acid + strong base no hydrolysis - neutral solutions KCl Strong acid + weak base hydrolysis to form acidic solution FeSO

Weak acid + strong base hydrolysis to form basic solution Na

CO

Weak acid + weak base Must use Ka and Kb to determine Pb(C

H

O

)

The commonly used strong acids are hydrochloric, nitric and sulfuric. The commonly used strong bases are sodium hydroxide, potassium hydroxide, and calcium hydroxide.

Predict the hydrolysis effect of each of the following salts. For each answer write acidic, basic neutral or need Ka and Kb.

____________________ 1. Na

PO

____________________ 2. Na

SO

____________________ 3. NaC

H

O

____________________ 4. NH

NO

____________________ 5. NH

Cl ____________________ 6. Fe

(PO

)

____________________ 7. Ca(NO

)

____________________ 8. KC

H

O

____________________ 9. CuSO

____________________ 10. Al(NO

)

____________________ 11. NaCl ____________________ 12. K

CO

Any oxygen-containing substance that will produce an acid when dissolved in water is called an acid anhydride. Any oxygen-containing substance that will produce a base when dissolved in water is called an basic anhydride. Anhydride means without water.

Metal oxides tend to form basic anhydrides and nonmetal oxides tend to form acidic anhydrides.

Predict the acidic or basic nature of the following anhydrides:

____________________ 13. CaO ____________________ 14. NO ____________________ 15. CO

____________________ 16. SO

____________________ 17. Na

O ____________________ 18. Rb

O Complete and balance the following:

19. CaO + H

O --->

20. CO

+ H

O --->

21. Na

O + H

O --->

22. SO

+ H

O --->

Determining the Strengths of Acids and Bases

If the statement is true, write “true”. If it is false change the underlined word(s) to make the statement true.

_________________ 1. A strong acid readily transfers H

ions to water to form hydronium ions.

_________________ 2. Strong acids are weak electrolytes.

_________________ 3. Substances that have the strongest affinity for hydrogen ions are strong bases.

_________________ 4. Weak acids do not completely ionize in water.

_________________ 5. The stronger an acid, the stronger its conjugate base.

_________________ 6. Salts are weak electrolytes.

Answer the following questions

7. What do acid and base dissociation constants measure?

8. What are salt-hydrolysis reactions?

9. Why is spilling 1 M acetic acid relatively harmless compared to spilling 1 M hydrochloric acid?

10. Defend or refute this statement: Strong acids are strong electrolytes.

11. Describe the relative strength of acids and their conjugate bases. Bases and their conjugate acids.

Kw/pH problems

1. What is the hydroxide ion concentration in saturated limewater if hydronium ion concentration = 3.98 x 10

M? Is limewater acidic, basic, or neutral?

2. What is the [H

O

] in a wheat flour and water solution if hydroxide ion concentration = 1.00 x 10

M? Is wheat flour and water acidic, basic, or neutral?

3. What is the hydronium ion concentration in 0.1 M ammonia if hydroxide ion concentration = 1.26 x 10

M? Is ammonia acidic, basic, or neutral?

4. What is the hydroxide ion concentration in butter if hydronium ion concentration = 6.00 x 10

M? Is butter acidic, basic, or neutral?

5. During the course of the day, human saliva varies between acidic and basic. What is the hydronium ion concentration in saliva if hydroxide ion concentration = 3.16 x 10

M? Is this sample of saliva acidic, basic, or neutral?

6. What is the [H

O

] in peaches if hydroxide ion concentration = 3.16 x 10

M? Are peaches acidic,

basic, or neutral?

7. What is the hydroxide ion concentration in 0.1 M bicarbonate of soda if hydronium ion concentration

= 3.98 x 10

M? Is bicarbonate of soda acidic, basic, or neutral?

8. A sample of human blood is found to have a hydronium ion concentration = 3.72 x 10

M? What is the pH of this sample? Is it acidic, basic, or neutral?

9. Analysis of samples of maple syrup reveals that the hydroxide ion concentration = 5.00 x 10

M.

What is the pH of this syrup? Is it acidic, basic, or neutral?

10. In a sample of bananas and water it was found that the hydronium ion concentration = 2.51 x 10

M. What is the pH of this sample? Is it acidic, basic, or neutral?

11. A soft drink was found to have a hydroxide ion concentration = 4.11 x 10

M? What is the pH of this soft drink? Is it acidic, basic, or neutral?

12. Tomatoes are found to have a hydronium ion concentration = 6.20 x 10

M? What is the pH of these tomatoes? Are they acidic, basic, or neutral?

13. A sample of urine is found to have a hydronium ion concentration = 6.30 x 10

M? What is the pH of this sample? Is it acidic, basic, or neutral?

14. In sour pickles the hydroxide ion concentration = 1.60 x 10

M. What is the pH of the pickles?

Are they acidic, basic, or neutral?

The self-ionization of Water and pH

Matching - On the line at the left, write the letter of the definition that best matches each term.

_____ 1. self-ionization a. has H

O

concentration greater than 1 x 10

M _____ 2. pure water b. has H

O

and OH

concentrations of 1 x 10

M _____ 3. ion-product constant c. has pH greater than 7

_____ 4. pH scale d. describes this reaction: H

O + H

O <---> H

O

+ OH

_____ 5. acidic solution e. has pH = 7; may contain ions other than H

O

+ OH

_____ 6. basic solution f. is equal to 1 x 10

at 25°C

_____ 7. neutral solution g. describes acidity or basicity of a solution 8. In pure water, what is the concentration of H

O

+ OH

ions? What is the pH?

9. The pH of a solution decreases from 9 to 7. How does the [H

O

] change? By what factor?

True or False - If the statement is true, write “true”. It is false, change the underlined word or words to make the statement true.

_________________ 10. In the reaction H

O + H

O <---> H

O

+ OH

, products are favored.

_________________ 11. The ion product constant applies to every water solution at a given temperature.

_________________ 12. An acidic solution contains only H

O

ions.

_________________ 13. A solution with a pH of 4 is acidic.

_________________ 14. A buffer is usually made up of a weak acid or base and its salt.

_________________ 15. An increase in the concentration of a buffer decreases the buffer capacity.

_________________ 16. The pH of a solution remains constant in the presence of a buffer if acid or a base is added beyond the buffer capacity.

_________________ 17. Adding OH

ions beyond the buffer capacity causes a decrease in the pH.

_________________ 18. All buffers have a limited capacity to neutralize H

O

+ OH

ions.

_________________ 19. Indicators are made from neutral solutions.

In each of the following situations, determine if the pH is decreased, increased or remains constant.

_________________ 20. Acid is added to a buffered solution until the buffer capacity is surpassed.

_________________ 21. Base is added to a buffered solution, not exceeding the buffer capacity.

_________________ 22. Base is added to a buffered solution, until the buffer capacity is surpassed.

_________________ 23. Acid is added to a buffered solution, not exceeding the buffer capacity.

24. What is the function of a buffer in blood? Why is it so important?

25. How can large changes in pH levels affect reactions?

26. What happens at the molecular level when an acid is added to a buffer solution? What about a base?

27. An acid is added to a buffer solution of acetic acid and its conjugate base. Write the equation for the reaction that occurs.

28. A base is added to a buffer solution of ammonia and its conjugate acid. Write the equation for the reaction that occurs

Titration Practice Problems

1. A volume of 30.0 mL of 0.25 M hydrochloric acid neutralizes a 50.0 mL sample of potassium hydroxide. What is the concentration of the potassium hydroxide?

2. A volume of 46.0 mL of 0.40 M sodium hydroxide neutralizes an 80.0 mL sample of hydrocyanic acid. What is the concentration of the hydrocyanic acid?

3. A volume of 90.0 mL of 0.20 M hydrobromric acid neutralizes a 60.0 mL sample of sodium

hydroxide. What is the concentration of the sodium hydroxide?

4. A volume of 50.0 mL of 0.30 M hydrochloric acid neutralizes a 60.0 mL sample of calcium hydroxide. What is the concentration of the calcium hydroxide?

5. A volume of 20.0 mL of 0.25 M Aluminum hydroxide neutralizes a 75.0 mL sample of sulfuric acid.

What is the concentration of the sulfuric acid?

6. A volume of 135.0 mL of 0.40 M hydrosulfuric acid neutralizes a 90.0 mL sample of aluminum hydroxide. What is the concentration of the aluminum hydroxide?

7. A mass of 2.91 g of hydrobromric acid neutralizes a 80.0 mL sample of calcium hydroxide. What is the concentration of the calcium hydroxide?

8. A total of 4.51 x 10

formula units of sodium hydroxide neutralizes a 30.0 mL sample of phosphorous acid. What is the concentration of the phosphorous acid?

Acids - Bases Titration

acid-base titration end point equivalence point indicator

phenolphthalein standard solution titration curve

1. The point at which exactly enough standard solution is added to neutralize the unknown solution is the ______________________.

2. A(n) ______________________ is used to represent pH data.

3. A(n) ______________________ is a carefully controlled neutralization reaction.

4. A(n) ______________________ changes color at certain pH values.

5. A(n) ______________________ contains an acid or a base in known concentration.

6. A common indicator used in titrations is ______________________.

7. The point at which the indicator changes color is the ______________________ of the reaction.

8. Why is it difficult to directly measure the concentration of a weak acid such as acetic acid?

9. How is an indicator useful in a titration?

10. Why should the end point of a titration be close to the equivalence point.

Acids and Bases - Review Activity

acid acid-base neutralization acid-base titration

acidic solution amphoteric substance base

basic solution Brönsted-Lowry definition buffer

conjugate pair dissociation end point

equivalence point hydrogen ion hydrolysis

hydronium ion hydroxide ion ion–product

ionization ionization constant indicator

logarithm neutral solution neutralization

nonelectrolyte pH proton acceptor

proton donor salt self–ionization

standard solution strong conjugate acid strong conjugate base

strong electrolyte weak conjugate acid weak conjugate base

weak electrolyte

A substance whose water solution does not conduct an electric current is called a(n) ________________. A substance whose water solution is a poor conductor is a (n) _____

_____________. One whose solution is a good conductor is a(n) ______ ____________. The ability to conduct an electric current can result from __________________, the action of water on ionic solids to produce and dispense hydrated ions. The ability to conduct can also result from ________________, the formation of charged particles by means of the reaction between water molecules and molecular substances.

According to Arrhenius, a(n) ____________ is a substance that, when mixed with water, produces the positively charged ____________ _______. This charged particle is hydrated by a water molecule, producing a(n) _____________ _______. The equilibrium constant for the formation of charged particles by an acid is called a(n) ___________ ___________ of the acid. According to the _________ __________ ____________, an acid is a(n) _________ __________ and a base is a(n) __________ __________. A substance that can act as either is called a(n) ____________

_____________.

An acid-base pair in which the acid and base are on opposite sides of an equation and are related by the transfer of a proton is called a(n) ____________ ______. A strong acid has a(n) ______

___________ _______, and a weak acid has a(n) _______ _____________ _________.

Salts of weak acids or weak bases can react with water in a process called

__________________. Water molecules can react with one another to produce charged particles in a process called _________– _____________. The quantity K

, which is the ______–_____________ for water, gives information on the concentration of these particles. The negative __________________ of the hydrogen-ion concentration is called the __________. The value of this quantity is greater than 7 in a(n) ________ ___________. Its value equals 7 in a(n) _________ _____________, and is less than 7 in a(n) _________ _____________.

A(n) ______________ is a mixture of a _________ acid and a _________ or a _________ base and a _________ that causes a solution to resist changes in its hydrogen-ion concentration. A(n)

________________ is a substance that changes color over a narrow range of hydrogen-ion concentrations.

Hydrogen ions combine with hydroxide ions during a reaction called ________–_________

_____________. A laboratory procedure that makes use of this reaction is called a(n) _______–

________ ________________. This procedure makes use of a solution of known concentration, called a(n) ___________ ___________. When enough of this solution has been added to react completely with the solution of unknown concentration, the _______________ _________ has been reached.

Acid/Base - Challenge Problems

1. What is the effect of dissolving potassium sulfite in a 0.100 M solution of sulfuric acid? Would you expect the acidity to increase or decrease? Describe a mechanism that explains your answer.

2. What is the pH of a saturated solution Iron(III) hydroxide? K

= 3.98 x 10

.

3. What is the pH of a 0.0100 M solution of Acetic Acid? K

= 1.75 x 10

.

4. What is the pH of a 0.150 M solution of the base diammine? K

= 8.71 x 10

5. What is the pH of a 0.650 M solution of Phosphoric Acid? K

(H

PO

) = 7.08 x 10

. K

(H

PO

) = 6.31 x 10

. K

(HPO

) = 4.17 x 10

.

6. You are titrating a 50.0 mL sample of hydrochloric acid with 0.250 M potassium hydroxide. After you have already added 42.3 mL of the potassium hydroxide you realize that you forgot to add the phenolphthalein indicator. When you add the indicator, the solution turns bright pink indicating that you have already missed the end point. You decide to “back-titrate” by adding 0.100 M nitric acid.

The solution turns colorless after an addition of 10.1 mL of the nitric acid. What is the concentration

of the original solution of hydrochloric acid.

7. What is the final pH of a solution that is made with acetic acid and of Copper(II) hydroxide in 1000.0 mL of solution in each of the following two situations.

K

acetic acid = 1.75 x 10

K

Copper(II) hydroxide = 2.19 x 10

a. 50.000 g of each solid b. 75.000 g of acid and 25.000 g base

Acid-Base Crossword

ACROSS DOWN

1. Number for which a given logarithm stands 2. Analytical method involving neutralization 3. One more oxygen 3. Acid that can donate more than one proton 6. Hydroxide ion formula 4. Describes a solution for which pH = 7 7. Scale for ranking hydronium ion concentrations 5. Naturally occurring acid in ants

8. Taste of bases 7. Commonly used indicator

9. Hydrated proton 8. Symbol for element 5

11 Hydrochloric acid formula 9. Ion released by many bases 13. Describes an acid containing one reacting

hydrogen atom.

10. Loss of electrons

12. Common name for calcium oxide 14. Contains 6.023 x 10

particles 16. Describes a strongly irritating basic

substance 15. Weak acid or base whose color depends on

hydronium ion concentration

18. A scientist who proposed an acid-base theory

17. Sodium hydroxide formula 19. Has formula NH

18. Symbol for element 18 20. Acid with formula HC

H

O

21. Describes species that are related by a

difference in protons

22. Acid with formula HNO

23. Mineral containing metal

24. Acid found in fruits

25. Scientist who created electron dot structures 26. Has pH less than 7

27. Charged atom

28. Symbol for element 16

4 3

1 2

5

6 7 8

9 10

11 12 17

13 18

14

15 16 19

20

21 22 23

25 27

24

26 28