Q: What is the pH of a solution with a hydrogen ion concentration of $5 \times 10^{-3}$ M?

$pH = -\log(5 \times 10^{-3}) = 2.30$

Question 1

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

Accepted Answer

A substance that donates a proton ($H^+$).

Question 2

What is the pH of a solution with a hydrogen ion concentration of $5 	imes 10^{-3}$ M?

Accepted Answer

$pH = -\log(5 	imes 10^{-3}) = 2.30$

Question 3

Which of the following statements about water is correct?

Accepted Answer

Water is amphoteric, meaning it can act as either an acid or a base.

Question 4

According to the Arrhenius definition, which of the following is a base?

Accepted Answer

A substance that produces $OH^-$ ions in water.

Question 5

A buffer solution is prepared using 0.10 M acetic acid ($CH_3COOH$) and 0.15 M sodium acetate ($CH_3COONa$). If the $pK_a$ of acetic acid is 4.76, what is the pH of the buffer?

Accepted Answer

$pH = 4.76 + \log(0.15/0.10) = 4.94$

Question 6

Which equation correctly represents the acid dissociation constant ($K_a$) for a weak acid $HA$?

Accepted Answer

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

Question 7

A patient’s blood pH drops from 7.4 to 7.0. What is the most likely physiological consequence?

Accepted Answer

The patient will experience acidosis.

Question 8

Which of the following best explains why buffers are important in biological systems?

Accepted Answer

Buffers maintain a constant pH, allowing enzymes and biochemical processes to function properly.

Question 9

If the $K_w$ (ion product of water) at 25°C is $1.0 	imes 10^{-14}$, what is the concentration of $H^+$ ions in pure water?

Accepted Answer

$[H^+] = 1.0 	imes 10^{-7}$ M

Question 10

Which of the following is true about strong acids?

Accepted Answer

They almost completely ionize in water to donate all their protons.

Question 11

A buffer solution contains 0.11 M acetic acid and 0.14 M acetate after addition of 0.01 M HCl. If the $pK_a$ of acetic acid is 4.76, what is the new pH?

Accepted Answer

$pH = 4.76 + \log(0.14/0.11) = 4.86$

Question 12

Which of the following is the correct Henderson-Hasselbalch equation for calculating the pH of a buffer?

Accepted Answer

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

Question 13

Which of the following pairs can act as a buffer solution?

Accepted Answer

Weak acid and its conjugate base

Question 14

What is the $pK_a$ of an acid with $K_a = 1.0 	imes 10^{-5}$?

Accepted Answer

$pK_a = -\log_{10}(1.0 	imes 10^{-5}) = 5$

Question 15

A solution has a pH of 10. What is the concentration of $OH^-$ ions?

Accepted Answer

$[OH^-] = 10^{-4}$ M

Question 16

Which of the following best describes the effect of adding a strong acid to a buffer solution?

Accepted Answer

The buffer neutralizes the added acid, causing only a small change in pH.

Question 17

Which of the following is a real-world example of a biological buffer system?

Accepted Answer

Carbonic acid-bicarbonate system in blood

Question 18

If a solution has a pH of 6, what is the hydrogen ion concentration?

Accepted Answer

$[H^+] = 10^{-6}$ M

Question 19

Which of the following statements about $pK_a$ is correct?

Accepted Answer

A smaller $pK_a$ value indicates a stronger acid.

Acids, Bases, and Buffers: Foundations and Applications in Chemistry

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