Q: A solution has a pH of 4. What is the concentration of hydronium ions ($$[H_3O^+]) in $$the solution?

$$[H_3O^+] = 1 \times 10$$^{-4}$$ M

Q: If the pH of a solution is 9, what is the concentration of hydroxide ions ($$[OH^-]$$)?

$$[OH^-] = 1 \times 10$$^{-5}$$ M

Question 1

Which of the following statements best describes a Lewis acid?

Accepted Answer

A substance that accepts an electron pair from another substance.

Question 2

A solution is prepared by dissolving 0.10 M acetic acid ($$CH_3COOH) in $$water. The acid dissociation constant is $$K_a = 1.8 	imes 10$$^{-5}$$. What is the pH of the solution? (Assume CH_3$$COOH$$ is a weak acid and ignore activity coefficients.)

Accepted Answer

pH $$\approx 3.0$$

Question 3

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

Sodium acetate ($$NaCH_3COO)$$

Question 4

Which equation is used to calculate the pH of a buffer solution?

Accepted Answer

$$pH = pK_a + \log \left( \frac{[A^-]}{[HA]} \right)$$

Question 5

A buffer is made by mixing 0.20 M $$NH_3$$ and 0.20 M $$NH_4Cl. $$What happens to the pH when a small amount of strong acid is added?

Accepted Answer

The pH decreases slightly.

Question 6

Which of the following acids is diprotic?

Accepted Answer

Sulfuric acid ($$H_2SO_4)$$

Question 7

Given the following $$K_a$$ values, which acid is the strongest?

Accepted Answer

$$K_a = 1.0 	imes 10$$^{-3}$$

Question 8

A solution has a pH of 4. What is the concentration of hydronium ions ($$[H_3O^+]) in $$the solution?

Accepted Answer

$$[H_3O^+] = 1 	imes 10$$^{-4}$$ M

Question 9

Which of the following is the conjugate base of $$HCO_3$$^-$$?

Accepted Answer

$$CO_3$$^{2-}$$

Question 10

A buffer solution is prepared using $$CH_3COOH$$ and $$CH_3COONa. If $$the concentration of $$CH_3COOH is $$doubled while $$CH_3COONa$$ remains constant, what happens to the pH?

Accepted Answer

The pH decreases.

Question 11

Which of the following best explains the common ion effect?

Accepted Answer

The addition of a common ion decreases the ionization of a weak acid or base.

Question 12

A 0.01 M solution of $$NaOH is $$prepared. What is the pOH of the solution?

Accepted Answer

pOH $$= 2$$

Question 13

Which of the following is NOT a property of a buffer solution?

Accepted Answer

It maintains a constant pH regardless of the amount of acid or base added.

Question 14

Which of the following reactions represents the completion of an acid-base reaction between $$HCl$$ and $$NaOH$$?

Accepted Answer

$$HCl + NaOH \rightarrow NaCl + H_2O$$

Question 15

A weak base $$B$$ has a $$K_b of$$ $$1.0 	imes 10$$^{-6}$$. If the initial concentration of B$ is 0.10 M, what is the approximate pOH of the solution?

Accepted Answer

pOH $$\approx 6$$

Question 16

Which of the following pairs can be used to make a buffer solution?

Accepted Answer

$$NH_3$$ and $$NH_4Cl$$

Question 17

If the pH of a solution is 9, what is the concentration of hydroxide ions ($$[OH^-]$$)?

Accepted Answer

$$[OH^-] = 1 	imes 10$$^{-5}$$ M

Question 18

Which of the following is the conjugate acid of $$NH_3$$?

Accepted Answer

$$NH_4$$^+$$

Question 19

A buffer solution is made from 0.50 M $$CH_3COOH$$ and 0.50 M $$CH_3COONa. If 0.01 $$mol of $$HCl is $$added to 1 L of this buffer, what happens to the pH?

Accepted Answer

The pH decreases slightly.

Acid-Base Equilibria and Buffers: Study Guide

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