PreLab Quiz: Experiment 7, Acid-Base Equilibria: Determination of Acid Ionization Constants

Which of the following indicates the most acidic solution?

Select one:

a. [H⁺] = 1.0 x 10^-4 M

b. pOH = 5.9

c. [OH^-] = 0.5 M

d. [H⁺] = 0.3 M

e. pH = 1.2

d. [H⁺] = 0.3 M

Calculate the hydrogen ion concentration for a solution of pH 8.4 .

Type answer:

3.98×10^-9 M

The acid dissociation constant, Ka, of acetic acid is 1.8 x 10-5. What is the pKa of this acid?

4.74

Consider the following reaction at equilibrium.

CH3COOH(aq) ⇌ CH3COO-(aq) + H+(aq)

When NaCH3COO is added to the solution will the value of the equilibrium constant, Ka and the pH of the solution increase, decrease, or remain the same?

Select one:

a. Ka remains the same and pH increases

b. Ka increases and pH decreases

c. Ka decreases and pH increases

d. Ka remains the same and pH decreases

e. Ka decreases and pH remains the same

a. Ka remains the same and pH increases

Calculate the pH of a 0.48 M solution of a weak acid, HA. For the acid, HA K =6.9x10^-8. Do not include units in your answer, If you round during your calculations make sure to keep at least 4 significant figures. Report your answer to three significant figures. 

3.74

When 29.9 mL of 0.100 M barium hydroxide is mixed with 97 mL of 0.200 M hydrochloric acid, the reaction goes to completion. Calculate the pH of the solution. 

Do not include units in your answer, If you round during your calculations make sure to keep at least 3 significant figures. Report your answer to two significant figures.

0.98

A 0.1 M CH3COOH solution is titrated with 0.1 M NaOH.

At what point in the titration will the pH of the solution be equal to the pKa?

Select one:

a. When the concentration [CH3COOH] = [CH3COO-].

b. At the equivalence point.

c. When the moles of CH3COOH(aq) equals the moles of OH-(aq).

d. When we observe a color change in the solution

e. None of the above

a. When the concentration [CH3COOH] = [CH3COO-].

Consider a weak acid, HA, for which K = 7.7x10^-4. Calculate [H ] in a solution that is 0.95 M in NaA and 0.81 M in HA.

Do not include units in your answer. Do not use scientific notation in your answer. If you round during your calculations make sure to keep at least 5 decimal places. Report your answer with two significant figures.

6.6×10^-4

Calculate the pH of a solution that contains 16.4 mL of 1.0 M NaCN, 29.5 mL of 1.0 M HCN and 7.7 mL of 1.0 M NaOH. Ka for HCN is 6.2 × 10−10.

9.25

For a generic acid, HA, K = 1.0 × 10−8. Calculate the pH of a solution made by mixing 31.3 mL of 0.340 M NaA with 25.1 mL of 0.100 M HCl.

Select one:

A. 8.95

B. 5.81

C. 7.31

D. 8.51

E. 4.76

D. 8.51

For the acid HA, the acid dissociation constant, K , is 9 × 10^-5 . After 34 mL of 0.8 M NaOH is added to 34 mL of a 1.6 M HA solution, what will the pH of the resulting solution be? 

Do NOT include units in your answer. If you round during your calculation, be sure to keep at least four significant figures. Report your answer to three significant figures.

4.05

Consider the generic weak acid HA, for which Ka = 1.2 × 10-5. Which of the following mixtures would result in a buffer solution when 30.0 mL of each of the two solutions are mixed?

Select one:

A. 0.10 M NaOH and 0.10 M HA

B. 0.20 M NaOH and 0.10 M HA

C. 0.10 M NaOH and 0.20 M HA

D. 0.01 M NaOH and 0.20 M HA

E. None of the above are correct

C. 0.10 M NaOH and 0.20 M HA