Acid and Base Worksheet - Answers



Acid and Base Worksheet - Answers

1) Using your knowledge of the Brønsted-Lowry theory of acids and bases, write equations for the following acid-base reactions and indicate each conjugate acid-base pair:

a) HNO3 + OH-1 ( H2O + NO3-1

HNO3 and NO3-1 make one pair OH-1 and H2O make the other

b) CH3NH2 + H2O ( CH3NH3+ + OH-1

CH3NH2 and CH3NH3+1 make one pair OH-1 and H2O make the other

c) OH-1 + HPO4-2 ( H2O + PO4-3

HPO4-2 and PO4-3 make one pair OH-1 and H2O make the other

2) The compound NaOH is a base by all three of the theories we discussed in class. However, each of the three theories describes what a base is in different terms. Use your knowledge of these three theories to describe NaOH as an Arrhenius base, a Brønsted-Lowry base, and a Lewis base.

• NaOH is an Arrhenius base because it creates OH-1 ions when placed in water.

• NaOH is a Brønsted-Lowry base because it accepts H+1 ions from acids.

• NaOH is a Lewis base because the lone pairs on the hydroxide ion can be donated to other compounds.

3) When hydrogen chloride reacts with ammonia, ammonium chloride is formed. Write the equation for this process, and indicate which of the reagents is the Lewis acid and which is the Lewis base.

HCl + NH3 ( NH4Cl

NH3 is a Lewis base because it uses its lone pair electrons to pull a hydrogen atom from hydrochloric acid.

HCl is a Lewis acid because it accepts electrons from NH3 when the H is transferred.HHH

4) Write an equation for each of the following reactions and indicate what each

reaction produces: (For each of the following oxides, indicate if it is an acid or basic anhydride).

a. Carbon dioxide and water

CO2 + H2O ( H2CO3

Acid anhydride

b. Sodium oxide and water

Na2O + H2O ( 2NaOH(aq)

Basic anhydride

c. Dichlorine trioxide and water

Cl2O3 + H2O ( 2HClO2

Acidic anhydride

d. Beryllium oxide and water

BeO + H2O ( Be(OH)2

Basic anhydride

5) Borane (BH3) is a basic compound, but doesn’t conduct electricity when you dissolve it in water. Explain this, based on the definitions of acids and bases that we discussed in class. Borane is a Lewis base, but a negligibly strong Brønsted-Lowry base.

6) Write the names for the following acids and bases:

a) KOH potassium hydroxide

b) H2Se hydroselenic acid

c) C2H3O2H acetic acid

d) Fe(OH)2 iron(II) hydroxide

e) HCN hydrogen cyanide or hydrocyanic acid

7) Write the formulas for the following chemical compounds (remember, you’ve still got a pop quiz coming up before the end of next week!)

a) ammonium sulfate (NH4)2SO4

b) cobalt (III) nitride CoN

c) carbon disulfide CS2

d) aluminum carbonate Al2(CO3)3

e) chlorine Cl2

8) Write the conjugate acid for each of the following:

a. HPO4-2 b. NO2-1 c. HS-1 d. S-2

a. H2PO4-1 b. HNO2 c. H2S d. HS-1

17. Identify the INCORRECT statement:

a. As the pH increases the hydroxide ion decreases.

b. As the pH increases the hydronium ion concentration decreases.

c. As the pH increases the Kw of water remains the same.

d. As the pH increases the product [H3O+][OH-] remains constant.

e. As the pH increases the solution becomes less acidic and more alkaline.

17. a

18. Write the conjugate base for each of the following:

a. H2S c. NH3

b. HS-1 d. H2SO3

18. a. HS-1 b. S-2 c. NH2-1 d. HSO3-1

pH practice - Answers

1) What is the pH and pOH of a 1.2 x 10-3 HBr solution?

pH: 2.9 pOH: 11.1

2) What is the pH and pOH of a 2.34 x 10-5 NaOH solution?

pOH: 4.6 pH: 9.4

3) What is the pH and pOH of a solution made by adding water to 15 grams of hydroiodic acid until the volume of the solution is 2500 mL?

pH: 1.6 pOH: 12.4

4) What is the pH and pOH of a solution that was made by adding 400 mL of water to 350 mL of 5.0 x 10-3 M NaOH solution?

pOH: 2.7 pH: 11.3

5) What is the pH and pOH of a solution with a volume of 5.4 L that contains 15 grams of hydrochloric acid and 25 grams of nitric acid?

pH: 0.82 pOH: 13.18

6) A swimming pool has a volume of one million liters. How many grams of HCl would need to be added to that swimming pool to bring the pH down from 7 to 4? (Assume the volume of the HCl is negligible) 3545 grams (100. moles)

7) What is an electrolyte? Which of the following will produce stronger electrolyte solutions,

strong acids and bases or weak acids and weak bases? If one was comparing two strong

acids or two strong bases, how would they determine which solution would produce a

stronger electrolyte solution?

An electrolyte is a substance that produces a large number of ions when dissolved in solution. Strong acids and bases would be stronger electrolytes because they produce more ions in solution than weak acids and bases. To compare two strong acids or two strong bases, one would compare the Ka and Kb values to determine which would be a stronger electrolyte. The larger the K value the stronger the electrolyte.

8) Write the dissociation reactions for the polyprotic acid, Arsenic acid (H3AsO4). Using the

following k values, label the k values for each reaction:

(ka1 = 5 x 10-3, ka2 = 8 x 10-8, ka3 = 6 x 10-10)

H3AsO4(aq) (( H2AsO4-1(aq) + H3O+1(aq) ka1 = 5 x 10-3

H2AsO4-1(aq) (( HAsO4-2(aq) + H3O+1(aq) ka2 = 8 x 10-8

HAsO4-2(aq) (( AsO4-3(aq) + H3O+1(aq) ka3 = 6 x 10-10

9) Using the following Ka values, place the following acids in order of increasing acid strength.

HClO4 ka = 1 x 107 HCN Ka = 4.93 x 10-10

CH3OOH ka = 1.76 x 10-5 HF Ka = 3.53 x 10-4

HCN, CH3OOH, HF, HClO4

10) Using the Ka values from above, calculate the Kb values and place the following bases in

order of increasing strength. (Kw = Ka x Kb)

ClO4-1, F-1, CH3OO-1, CN-1

11) Indicate whether the following salts will produce an acidic, basic, or neutral solution when

dissolved in water.

a. Neutral b. acidic c. basic

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