Question

1. Which equilibrium is most important in determining the pH of a solution of sodium phosphate?

a. HPO₄^2- + H₂O = PO₄^3- + H₃O+

b. H₂PO₄^2- + H₂O = H₃PO₄ + OH^-

c. H₃PO₄ + H₂O = H₂PO₄^- + H₃O+

d. PO₄^3- + H₂O = HPO₄^2- + OH^-

2. Tina has two aqueous solutions: 1.2 x 10^-2 M NaOH and 1.2 x 10^-2 M NH₃ (K_B=1.8x10^-5). Which solution has the higher pH?

a. the NaOH solution
b. the ammonia solution
c. the solutions have the same pH

3. A 0.10 M solution of weak acid HA has a pH of 4.5. What is its K_a value?

a. 1.0 x 10^-8 b. 1.0 x 10^-6 c. 1.0 x 10^-7 d. 1.0 x 10^-10

4. Identify all of the corrects tatements about an acid-base buffer solution (please explain this one)

I. It can be prepared by combining a strong acid with a salt of its conjugate base.

II. It can be prepared by combining a weak acid with a salt of its conjugate base.

III. It can be prepared by combining a weak base with its conjugate acid.

IV. The pH of a buffer solution does not change when the solution is diluted.

V. An appropriate buffer solution resists changes in its pH when an acid or base is added to it.

a. I, II, and IV b. I, II, IV, and V c. II, III, IV, and V d. I, II and III

Answer 1

1.

d. PO43- + H2O = HPO42- + OH-

2.

The NaOH solution. it is strong base.

4.

II. It can be prepared by combining a weak acid with a salt of its conjugate base.

III. It can be prepared by combining a weak base with its conjugate acid.

IV. The pH of a buffer solution does not change when the solution is diluted.

V. An appropriate buffer solution resists changes in its pH when an acid or base is added to it.

c. II, III, IV, and V

3.