$$pH = -\log(2.5 \times 10$$^{-5}$$) = 4.60$$

$$[OH^-] = \frac{1.0 \times 10$$^{-14}$$}{1.0 \times 10$$^{-6}$$} = 1.0 \times 10$$^{-8}$$ M

$$V_{NaOH} = \frac{M_{HCl} \times V_{HCl}}{M_{NaOH}} = \frac{0.100 \times 25.0}{0.200} = 12.5 mL$$

Question 1

Which of the following best describes a Brønsted-Lowry acid?

Accepted Answer

A substance that donates a proton (H$$^+) to $$another molecule or ion

Question 2

Which of the following acids is diprotic?

Accepted Answer

H$$_2SO$_4$$

Question 3

What is the conjugate base of HCOOH (formic acid)?

Accepted Answer

HCOO$$^-$$

Question 4

Which of the following statements about strong acids is correct?

Accepted Answer

Strong acids give up a proton easily and are essentially 100% dissociated in water.

Question 5

Given the reaction: $$\mathrm{NH_3$(aq) + H_2O(l) \rightleftharpoons NH_4$^+(aq) + OH^-(aq)}$$, which species acts as the Brønsted-Lowry base?

Accepted Answer

$$\mathrm{NH_3$}$$

Question 6

A solution has $$[H_3O^+] = 2.5 	imes 10$$^{-5}$$ M. What is its pH?

Accepted Answer

$$pH = -\log(2.5 	imes 10$$^{-5}$$) = 4.60$$

Question 7

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

Accepted Answer

NaCN

Question 8

What is the $$[OH^-] in a $$solution where $$[H_3O^+] = 1.0 	imes 10$$^{-6}$$ M at 25$$^\circ$$C?

Accepted Answer

$$[OH^-] = \frac{1.0 	imes 10$$^{-14}$$}{1.0 	imes 10$$^{-6}$$} = 1.0 	imes 10$$^{-8}$$ M

Question 9

Which buffer system would be most effective at maintaining a pH near 4.1?

Accepted Answer

Ascorbic acid/ascorbate ($$pK_a = 4.10)$$

Question 10

A buffer solution contains 0.10 M HF and 0.20 M NaF. The $$K_a$$ for HF is $$3.5 	imes 10$$^{-4}$$. What is the pH of the buffer?

Accepted Answer

$$pH = 3.46 + \log\left(\frac{0.20}{0.10}\right) = 3.76$$

Question 11

Which of the following equations correctly represents the neutralization reaction between hydrochloric acid and potassium hydroxide?

Accepted Answer

$$\mathrm{HCl(aq) + KOH(aq) \rightarrow H_2O(l) + KCl(aq)}$$

Question 12

A 25.0 mL sample of 0.100 M HCl is titrated with 0.200 M NaOH. What volume of NaOH is required to reach the equivalence point?

Accepted Answer

$$V_{NaOH} = \frac{M_{HCl} 	imes V_{HCl}}{M_{NaOH}} = \frac{0.100 	imes 25.0}{0.200} = 12.5 mL$$

Question 13

Which of the following best explains why the pH of blood remains relatively constant even when small amounts of acid or base are added?

Accepted Answer

Blood contains a buffer system composed of a weak acid and its conjugate base.

Question 14

Which of the following is true about the relationship between acid strength and conjugate base strength?

Accepted Answer

The stronger the acid, the weaker its conjugate base.

Question 15

A solution has a pH of 9. What is the $$[H_3O^+]$$ concentration?

Accepted Answer

$$[H_3O^+] = 1 	imes 10$$^{-9}$$ M

Question 16

Which of the following is the correct expression for the acid dissociation constant ($$K_a) $$for a weak acid HA?

Accepted Answer

$$K_a = \frac{[H_3O^+][A^-]}{[HA]}$$

Question 17

A 0.020 mol sample of NaOH is added to 1.00 L of a buffer containing 0.100 M HF and 0.120 M NaF ($$pK_a = 3.46). $$What is the new pH?

Accepted Answer

$$pH = 3.46 + \log\left(\frac{0.140}{0.080}\right) = 3.70$$

Chapter 10: Acids and Bases – GOB Chemistry Study Notes

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