Q: Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

$$\text{pH} = \text{p}K_a + \log \frac{[\text{base}]}{[\text{acid}]}$$

Q: Which acid would you choose to combine with its sodium salt to make a solution buffered at pH 4.25?

Acid with $$\text{p}K_a$$ closest to 4.25

Q: Which ion in a buffer solution of acetic acid and sodium acetate will neutralize any addition of base?

Acetate ion ($$\text{CH}_3\text{COO}^-)$$

Q: What is the formula for the formation constant ($$K_f) of $$the complex ion Ag(NH$$_3$$)$$_2$$^{+}$$?

$$K_f = \frac{[\text{Ag(NH}_3)_2^+]}{[\text{Ag}^+][\text{NH}_3]^2}$$

Question 1

Which equation is used to calculate the pH of a buffer solution containing a weak acid and its conjugate base?

Accepted Answer

$$	ext{pH} = 	ext{p}K_a + \log \frac{[	ext{base}]}{[	ext{acid}]}$$

Question 2

A buffer solution is prepared by mixing 0.10 mol of acetic acid and 0.10 mol of sodium acetate in 1.0 L of water. What will happen to the pH if 0.010 mol of NaOH is added, assuming negligible volume change?

Accepted Answer

The pH will increase slightly due to the neutralization of acetic acid by NaOH.

Question 3

Which acid would you choose to combine with its sodium salt to make a solution buffered at pH 4.25?

Accepted Answer

Acid with $$	ext{p}K_a$$ closest to 4.25

Question 4

What is the pH of a solution that is 0.200 M in NH3 and 0.300 M in NH4Cl? ($$	ext{p}K_b of NH3 = 4.75)$$

Accepted Answer

$$	ext{pH} = 9.06$$

Question 5

Which ion in a buffer solution of acetic acid and sodium acetate will neutralize any addition of base?

Accepted Answer

Acetate ion ($$	ext{CH}_3	ext{COO}^-)$$

Question 6

A buffer is most effective when the concentrations of acid and conjugate base are:

Accepted Answer

Equal

Question 7

What is the initial pH of a 25.0 mL solution of 0.100 M HCl?

Accepted Answer

$$	ext{pH} = 1.00$$

Question 8

During a titration, the equivalence point is reached when:

Accepted Answer

The number of moles of acid equals the number of moles of base

Question 9

What is the molar solubility of PbCl$$_2 in $$pure water given $$K_{sp} = 1.17 	imes 10$$^{-5}$$?

Accepted Answer

$$1.62 	imes 10$$^{-2}$$ M

Question 10

If $$Q \u003c K_{sp}$$ for a salt in solution, what will happen?

Accepted Answer

No precipitate will form; the solution is unsaturated.

Question 11

Which compound is more soluble in an acidic solution than in a neutral solution?

Accepted Answer

BaF$$_2$$

Question 12

What is the effect of adding a strong Lewis base like ammonia to a solution containing Ag(H$$_2O$$)$$_2$$^{+}$$?

Accepted Answer

The ammonia will displace water, forming Ag(NH$$_3$$)$$_2$$^{+}$$.

Question 13

What is the formula for the formation constant ($$K_f) of $$the complex ion Ag(NH$$_3$$)$$_2$$^{+}$$?

Accepted Answer

$$K_f = \frac{[	ext{Ag(NH}_3)_2^+]}{[	ext{Ag}^+][	ext{NH}_3]^2}$$

Question 14

A solution contains 0.0150 M lead(II) nitrate and 0.0035 M sodium bromide. Will a precipitate form if $$K_{sp}$$ for PbBr$$_2 is$$ $$4.67 	imes 10$$^{-6}$$?

Accepted Answer

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

Question 15

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity increases as the concentrations of acid and conjugate base increase.

Question 16

What is the pH at the equivalence point in the titration of 0.10 M NH$$_3$$ with HCl?

Accepted Answer

$$	ext{pH} = 5.26$$

Question 17

For a polyprotic acid with $$K_{a1} = 1.6 	imes 10$$^{-2}$$ and K$$_{a2} = 6.4 	imes $$10^{-8}$$, which statement is true?

Accepted Answer

The first proton is much easier to remove than the second.

Question 18

Why should $$K_{sp}$$ not be used to compare the relative solubilities of two different compounds?

Accepted Answer

Because the relationship between $$K_{sp}$$ and solubility depends on the stoichiometry of the compound.

Aqueous Ionic Equilibrium: Buffers, Titrations, and Solubility

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