Q: Which of the following is the correct expression for the percent ionization of a weak acid?

$$\frac{[\mathrm{H^+}]}{[\text{initial acid}]} \times 100\%$$

Q: If the $$K_b$$ for ammonia ($$\mathrm{NH_3$}) is$$ $$1.8 \times 10$$^{-5}$$, what is the K_a$ for its conjugate acid ($$\mathrm{$$NH_4$$^+}$$)? (K_w = 1.0$$ \times $$10^{-14})$$

$$K_a = 5.6 \times 10$$^{-10}$$

Q: A $$0.050\ \mathrm{M}$$ solution of $$\mathrm{$$HNO_2$$}$$ has a $$K_a of$$ $$4.5 \times 10$$^{-4}$$. What is the concentration of $$\mathrm{H^+}$$ ions at equilibrium?

$$1.5 \times 10$$^{-3}$$\ \mathrm{M}$$

Q: Which of the following is the correct formula for the Henderson-Hasselbalch equation?

$$\mathrm{pH} = \mathrm{p}K_a + \log\left(\frac{[\text{base}]}{[\text{acid}]}\right)$$

Question 1

What is the conjugate base of $$\mathrm{$$HPO_4$$^{2-}}$$?

Accepted Answer

$$\mathrm{PO_4$^{3-}}$$

Question 2

Which of the following is NOT a conjugate acid/base pair?

Accepted Answer

$$\mathrm{C_2H_3O_2^-}/\mathrm{HC_2H_3O_2}$$

Question 3

Calculate the pH of a solution that contains $$7.8 	imes 10$$^{-4}$$\ \mathrm{M}\ \mathrm{OH^-}.$$

Accepted Answer

12.72

Question 4

Find the percent ionization of a $$0.337\ \mathrm{M} HF $$solution. The $$K_a$$ for HF is $$3.5 	imes 10$$^{-4}$$.

Accepted Answer

3.2\%

Question 5

A buffer solution is made by mixing $$0.2\ \mathrm{mol} of $$acetic acid ($$\mathrm{HC_2H_3O_2}) $$and $$0.2\ \mathrm{mol} of $$sodium acetate ($$\mathrm{NaC_2H_3O_2}) in$$ $$1.0\ \mathrm{L} of $$water. If the $$K_a of $$acetic acid is $$1.8 	imes 10$$^{-5}$$, what is the pH of the buffer?

Accepted Answer

$$\mathrm{pH} = 4.74$$

Question 6

Which of the following statements about strong acids is correct?

Accepted Answer

Strong acids ionize completely in water.

Question 7

A solution is prepared by dissolving $$0.1\ \mathrm{mol} of$$ $$\mathrm{NH_4Cl} in$$ $$1.0\ \mathrm{L} of $$water. What is the effect on the pH compared to pure water?

Accepted Answer

The pH decreases because $$\mathrm{NH_4$^+} is a $$weak acid.

Question 8

Which of the following is the correct expression for the percent ionization of a weak acid?

Accepted Answer

$$\frac{[\mathrm{H^+}]}{[	ext{initial acid}]} 	imes 100\%$$

Question 9

If the $$K_b$$ for ammonia ($$\mathrm{NH_3$}) is$$ $$1.8 	imes 10$$^{-5}$$, what is the K_a$ for its conjugate acid ($$\mathrm{$$NH_4$$^+}$$)? (K_w = 1.0$$ 	imes $$10^{-14})$$

Accepted Answer

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

Question 10

A $$0.050\ \mathrm{M}$$ solution of $$\mathrm{$$HNO_2$$}$$ has a $$K_a of$$ $$4.5 	imes 10$$^{-4}$$. What is the concentration of $$\mathrm{H^+}$$ ions at equilibrium?

Accepted Answer

$$1.5 	imes 10$$^{-3}$$\ \mathrm{M}$$

Question 11

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

Accepted Answer

$$\mathrm{NaF}$$

Question 12

A patient is suffering from metabolic acidosis. Which of the following best describes the chemical imbalance?

Accepted Answer

Blood pH is lower than normal due to excess $$\mathrm{H^+}.$$

Question 13

Which of the following equations correctly relates pH and pOH?

Accepted Answer

$$\mathrm{pH} + \mathrm{pOH} = 14$$

Question 14

Which of the following is the correct formula for the Henderson-Hasselbalch equation?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log\left(\frac{[	ext{base}]}{[	ext{acid}]}ight)$$

Question 15

A $$0.10\ \mathrm{M}$$ solution of $$\mathrm{NaOH} is $$accidentally spilled in a laboratory. What is the pH of the solution?

Accepted Answer

13.00

Question 16

Which of the following is a real-life example of a buffer system in the human body?

Accepted Answer

The $$\mathrm{CO_2$}/\mathrm{$$HCO_3$$^-}$$ system in blood

Question 17

Which of the following acids is considered a weak acid?

Accepted Answer

$$\mathrm{HF}$$

Question 18

A $$0.25\ \mathrm{M}$$ solution of $$\mathrm{CH_3COOH}$$ has a $$K_a of$$ $$1.8 	imes 10$$^{-5}$$. What is the pH of the solution?

Accepted Answer

4.74

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