Q: Which of the following salts will have the lowest molar solubility in pure water?

$AB$ with $K_{sp} = 1 \times 10^{-10}$

Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution containing a weak acid and its conjugate base in comparable concentrations.

Question 2

What is the Henderson-Hasselbalch equation for calculating the pH of a buffer solution?

Accepted Answer

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

Question 3

A buffer is most effective when:

Accepted Answer

The concentrations of acid and base are equal.

Question 4

Which of the following is the correct expression for the equilibrium constant $K_{sp}$ for the dissolution of $PbCl_2$?

Accepted Answer

$K_{sp} = [Pb^{2+}][Cl^-]^2$

Question 5

If you add a small amount of strong acid to a buffer solution, what happens?

Accepted Answer

The buffer neutralizes the acid, causing only a slight decrease in pH.

Question 6

Calculate the pH of a buffer solution containing 0.10 M acetic acid ($CH_3COOH$) and 0.10 M sodium acetate ($NaCH_3COO$). The $pK_a$ of acetic acid is 4.76.

Accepted Answer

pH = 4.76

Question 7

Which of the following buffer systems would be most effective at maintaining a pH near 9?

Accepted Answer

Phenol/phenoxide ($pK_a = 9.99$)

Question 8

During the titration of a weak acid with a strong base, the pH at the half-equivalence point is:

Accepted Answer

Equal to the $pK_a$ of the acid

Question 9

A buffer solution is prepared by mixing 0.50 mol of $NH_3$ and 0.20 mol of $NH_4Cl$ in 1.0 L of water. What is the pH of the solution? ($pK_b$ for $NH_3$ = 4.75)

Accepted Answer

pH = 9.23

Question 10

Which statement about buffer capacity is correct?

Accepted Answer

Buffer capacity is highest when the concentrations of acid and base are large and equal.

Question 11

A solution contains 0.175 M $HF$ and 0.200 M $NaF$. What is the pH of the solution? ($pK_a$ of $HF$ = 3.17)

Accepted Answer

pH = 3.25

Question 12

Which of the following best explains why the equivalence point of a strong acid-strong base titration is at pH 7?

Accepted Answer

The salt formed is neutral and does not hydrolyze in water.

Question 13

For the dissolution of $AB_2(s)$, the $K_{sp}$ expression is:

Accepted Answer

$K_{sp} = [A^{2+}][B^-]^2$

Question 14

A buffer solution is made by mixing 0.10 mol $CH_3COOH$ and 0.10 mol $NaCH_3COO$ in 1.0 L of water. What will happen to the pH if 0.01 mol $HCl$ is added?

Accepted Answer

The pH will decrease slightly due to the buffer action.

Question 15

Which of the following salts will have the lowest molar solubility in pure water?

Accepted Answer

$AB$ with $K_{sp} = 1 	imes 10^{-10}$

Question 16

Which of the following will increase the solubility of $Mg(OH)_2$ in water?

Accepted Answer

Adding $H^+$ ions.

Question 17

A solution is made by mixing 0.10 M $Ba^{2+}$ and 0.020 M $Ca^{2+}$ with $OH^-$ ions. Which cation will precipitate first as the $OH^-$ concentration increases?

Accepted Answer

$Ca^{2+}$

Question 18

Which of the following statements about the buffer range is correct?

Accepted Answer

A buffer is effective when $0.1 < [\mathrm{base}]/[\mathrm{acid}] < 10$.

Question 19

During a titration of a weak acid with a strong base, what is the pH at the equivalence point?

Accepted Answer

Greater than 7

Buffers, Titrations, and Solubility Equilibria: Study Notes for General Chemistry

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