Q: Which equation is used to calculate the pH of a buffer solution?

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

Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution made from a weak acid and its conjugate base, or a weak base and its conjugate acid.

Question 2

A buffer is most effective when:

Accepted Answer

The concentrations of acid and base are equal and the pH is close to the pKa.

Question 3

Which equation is used to calculate the pH of a buffer solution?

Accepted Answer

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

Question 4

A buffer is prepared by mixing 0.10 mol of acetic acid ($$\mathrm{CH_3COOH}) $$and 0.10 mol of sodium acetate ($$\mathrm{CH_3COONa}) in 1.0 L of $$water. If the $$\mathrm{p}K_a of $$acetic acid is 4.76, what is the pH of the buffer?

Accepted Answer

4.76

Question 5

Which of the following changes will DESTROY a buffer solution?

Accepted Answer

Adding enough strong acid or base to eliminate one buffer component.

Question 6

You want to prepare a buffer with a pH of 9.0. Which acid-base pair would be most appropriate?

Accepted Answer

A weak acid with $$\mathrm{p}K_a = 9.0$$ and its conjugate base.

Question 7

During a titration of a weak acid with a strong base, the equivalence point will be:

Accepted Answer

Above pH 7

Question 8

Which statement about the titration curve of a strong acid with a strong base is correct?

Accepted Answer

The equivalence point occurs at pH = 7.

Question 9

A solution contains 0.10 M $$\mathrm{CH_3COOH}$$ and 0.10 M $$\mathrm{CH_3COONa}. If 0.01 $$mol of HCl is added to 1.0 L of this buffer, what will happen to the pH?

Accepted Answer

The pH will decrease slightly.

Question 10

Which of the following best describes the equivalence point in a titration?

Accepted Answer

The point where the amount of titrant added exactly reacts with all of the analyte.

Question 11

What is the solubility product constant ($$K_{sp}) $$expression for $$\mathrm{$$CaF_2$$}$$?

Accepted Answer

$$K_{sp} = [\mathrm{Ca}^{2+}][\mathrm{F}^-]^2$$

Question 12

If the reaction quotient $$Q$$ for a sparingly soluble salt is greater than $$K_{sp}$$, what will happen?

Accepted Answer

A precipitate will form.

Question 13

Which of the following will increase the solubility of a sparingly soluble salt containing $$\mathrm{CO_3$^{2-}}$$?

Accepted Answer

Adding a strong acid to the solution.

Question 14

Which of the following is TRUE about the half-equivalence point in a titration of a weak acid with a strong base?

Accepted Answer

The pH equals the $$\mathrm{p}K_a of $$the acid.

Question 15

A buffer is made by mixing 0.20 mol of $$\mathrm{NH_4Cl}$$ and 0.10 mol of $$\mathrm{NH_3$} in 1.0 L of $$water. If the $$\mathrm{p}K_b of$$ $$\mathrm{NH_3$} is 4.75$$, what is the pH of the buffer? (Assume $$\mathrm{p}K_w = 14)$$

Accepted Answer

8.75

Question 16

Which of the following is a correct application of the common ion effect?

Accepted Answer

Adding $$\mathrm{NaCl} to a $$solution of $$\mathrm{AgCl}$$ decreases the solubility of $$\mathrm{AgCl}.$$

Question 17

During the titration of a weak base with a strong acid, the equivalence point will be:

Accepted Answer

Below pH 7

Question 18

Which of the following is the best way to choose a buffer for a desired pH?

Accepted Answer

Choose a weak acid or base whose $$\mathrm{p}K_a or$$ $$\mathrm{p}K_b is $$close to the desired pH.

Question 19

A solution is prepared by mixing 50.0 mL of 0.10 M $$\mathrm{$$AgNO_3$$}$$ and 50.0 mL of 0.10 M $$\mathrm{NaCl}. $$Will a precipitate form? ($$K_{sp}$$ for $$\mathrm{AgCl} is$$ $$1.8 	imes 10$$^{-10}$$)

Accepted Answer

Yes, because $$Q \u003e K_{sp}.$$

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