Q: Which equation is used to determine if a precipitate will form when two solutions are mixed?

$$Q = [\text{products}]^n/[\text{reactants}]^m$$ and compare to $$K_{sp}$$

Question 1

Which of the following best describes a buffer solution?

Accepted Answer

A solution that contains a weak acid and its conjugate base, resisting changes in pH when small amounts of acid or base are added.

Question 2

Given a buffer solution containing 1.0 M HF and 0.5 M NaF, what is the correct way to calculate its pH?

Accepted Answer

Use the Henderson-Hasselbalch equation: $$pH = pK_a + \log_{10} \left( \frac{[A^-]}{[HA]} \right)$$

Question 3

What happens to the value of $$K_a$$ for HF if NaF is added to the solution at constant temperature?

Accepted Answer

$$K_a$$ remains the same

Question 4

A buffer solution is prepared by mixing 40 mL of 1.0 M HF and 0.5 M NaF. If 2.0 mL of 1.0 M NaOH is added, what is the first step in calculating the new pH?

Accepted Answer

Calculate the moles of HF, NaF, and NaOH and perform a stoichiometry (before and after) table.

Question 5

Which of the following mixtures will NOT result in a buffer solution?

Accepted Answer

A mixture of 1.0 M HCl and 1.0 M NaCl

Question 6

During the titration of 50 mL of 1.0 M CH$$_3$$COOH with 1.0 M NaOH, what is the pH at the half-equivalence point?

Accepted Answer

pH = pK_a

Question 7

Refer to the first titration curve image. What does the steepest part of the curve represent?

Accepted Answer

The equivalence point, where all acid has been neutralized by base

Question 8

A solution is made by mixing 40.0 mL of 1.0 M HCl with 30.0 mL of 1.0 M Ba(OH)$$_2. $$What is the resulting solution?

Accepted Answer

Basic

Question 9

Which of the following best explains why the pH at the equivalence point in the titration of acetic acid with NaOH is greater than 7?

Accepted Answer

The salt formed (sodium acetate) hydrolyzes to produce OH$$^-$$ ions.

Question 10

Which equation is used to determine if a precipitate will form when two solutions are mixed?

Accepted Answer

$$Q = [	ext{products}]^n/[	ext{reactants}]^m$$ and compare to $$K_{sp}$$

Question 11

What is the effect of adding 0.1 M AgNO$$_3 to a $$saturated solution of Ag$$_2SO$_4$$?

Accepted Answer

The solubility of Ag$$_2SO$_4$$ decreases.

Question 12

Which of the following is the correct net ionic equation for the titration of acetic acid with NaOH?

Accepted Answer

$$\mathrm{CH_3COOH} + \mathrm{OH^-} \rightarrow \mathrm{CH_3COO^-} + \mathrm{H_2O}$$

Question 13

A student wants to prepare 250 mL of a buffer solution at pH = 7.20 using 1.0 M HClO and solid NaClO (74.44 g/mol). What equation should they use to determine the amount of NaClO needed?

Accepted Answer

Henderson-Hasselbalch equation: $$pH = pK_a + \log_{10} \left( \frac{[	ext{ClO}^-]}{[	ext{HClO}]} ight)$$

Question 14

Which of the following statements about the buffer region in a titration curve is correct?

Accepted Answer

The buffer region occurs before the equivalence point, where both weak acid and its conjugate base are present.

Question 15

For the titration of a polyprotic acid such as H$$_3PO$_4$$, what does each equivalence point on the titration curve represent?

Accepted Answer

The complete neutralization of one acidic proton by base.

Question 16

Which of the following best describes the common ion effect?

Accepted Answer

The decrease in solubility of an ionic compound when a common ion is added to the solution.

Question 17

If $$K_{sp} \u003e Q$$ for a solution, what will happen?

Accepted Answer

No precipitate will form.

Question 18

Which of the following is true about the use of the Henderson-Hasselbalch equation?

Accepted Answer

It can only be used for buffer solutions where $$0.1 \u003c \frac{[A^-]}{[HA]} \u003c 10.$$

Acid-Base Equilibria, Buffers, and Solubility Equilibria

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