Q: Which of the following is a correct expression for the percent ionization of a weak base $$B in $$water?

$$\frac{[OH^-]_{eq}}{[B]_i} \times 100$$

Question 1

Which of the following statements best describes the relationship between the acid dissociation constant ($$K_a) of a $$weak acid and the base dissociation constant ($$K_b) of $$its conjugate base in aqueous solution?

Accepted Answer

$$K_a 	imes K_b = K_w$$

Question 2

A 0.20 M solution of formic acid ($$HCHO_2) $$has a pH of 2.22. What is the percent ionization of formic acid in this solution?

Accepted Answer

3.0%

Question 3

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

Accepted Answer

$$NaCHO_2$

Question 4

Given $$K_b$$ for ammonia ($$NH_3) is$$ $$1.8 	imes 10$$^{-5}$$, what is the K_a$ for its conjugate acid (NH_4$^+$$)?

Accepted Answer

$$5.6 	imes 10$$^{-10}$$

Question 5

Which of the following is a correct expression for the percent ionization of a weak base $$B in $$water?

Accepted Answer

$$\frac{[OH^-]_{eq}}{[B]_i} 	imes 100$$

Question 6

A solution is prepared by dissolving 0.975 g of acetylsalicylic acid (ASA, $$HC_9H_7O_4) in $$enough water to make 356 mL of solution. Given $$K_a = 3.30 	imes 10$$^{-4}$$ and MW = 180.160$ g/mol, what is the initial molarity of ASA?

Accepted Answer

0.0152 M

Question 7

Which of the following best explains why the assumption that $$x is $$negligible compared to the initial concentration is not valid when calculating the pH of a weak acid solution if the percent ionization is greater than 5%?

Accepted Answer

Because the change in concentration is significant and affects the equilibrium calculation.

Question 8

Which of the following weak bases has the highest $$K_b$$ value and thus is the strongest base among the options?

Accepted Answer

Methylamine ($$CH_3NH_2)$$

Question 9

A 0.30 M solution of dimethylamine ($$ (CH_3$)_2NH ) $$has a $$K_b of$$ $$5.9 	imes 10$$^{-4}$$. What is the pH of this solution?

Accepted Answer

12.11

Question 10

Which of the following cations will NOT affect the pH of an aqueous solution?

Accepted Answer

$$Na^+$$

Question 11

A solution of $$NH_4Br is $$prepared at 0.20 M. Given $$K_b$$ for ammonia is $$1.8 	imes 10$$^{-5}$$, what is the pH of the solution? (Use K_w = 1.0$$ 	imes $$10^{-14})$$

Accepted Answer

4.96

Question 12

Which of the following anions is pH-neutral in water?

Accepted Answer

$$Cl^-$$

Question 13

If a salt solution contains a cation from a weak base and an anion from a weak acid, what determines whether the solution is acidic, basic, or neutral?

Accepted Answer

The relative values of $$K_a$$ and $$K_b$$ for the cation and anion

Question 14

Which of the following best describes the effect of a small, highly charged metal ion (such as $$Al^{3+}) on $$the pH of an aqueous solution?

Accepted Answer

It makes the solution acidic by increasing $$[H_3O^+]$$ through hydrolysis.

Question 15

Calculate the $$K_b$$ for the acetate ion ($$C_2H_3O_2^-) $$given that the $$K_a$$ for acetic acid is $$1.8 	imes 10$$^{-5}$$.

Accepted Answer

$$5.6 	imes 10$$^{-10}$$

Question 16

A 0.20 M solution of sodium formate ($$NaCHO_2) is $$prepared. Given $$K_a$$ for formic acid is $$1.8 	imes 10$$^{-4}$$, what is the pH of the solution?

Accepted Answer

8.52

Question 17

Which of the following is the correct formula for calculating the pOH of a solution given the hydroxide ion concentration?

Accepted Answer

$$pOH = -\log[OH^-]$$

Question 18

Which of the following best explains why the solution of $$NH_4F is $$slightly acidic?

Accepted Answer

Because $$K_a of$$ $$NH_4$$^+$$ is greater than K_b$ of F$$^-$$

Acids, Bases, and the Acid-Base Properties of Salt Solutions

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