Q: The solubility product constant ($$K_{sp}) $$for $$\mathrm{$$BaSO_4$$} is$$ $$1.1 \times 10$$^{-10}$$. What is the molar solubility of $$\mathrm{$$BaSO_4$$}$$ in pure water?

$$1.0 \times 10$$^{-5}$$~\mathrm{mol/L}$$

Question 1

Which of the following best describes the common-ion effect as it applies to the equilibrium of acetic acid in the presence of sodium acetate?

Accepted Answer

The addition of sodium acetate shifts the equilibrium to the left, decreasing [H+].

Question 2

A buffer solution is prepared by mixing 0.20 mol of NH4Cl and 0.20 mol of NH3 in enough water to make 1.0 L of solution. Which equation would you use to calculate the pH of this buffer?

Accepted Answer

$$\mathrm{pOH} = \mathrm{p}K_b + \log\left(\frac{[\mathrm{NH}_4^+]}{[\mathrm{NH}_3]}\right)$$

Question 3

Which of the following statements about buffer capacity is correct?

Accepted Answer

A buffer with higher concentrations of acid and base can neutralize more added acid or base before a significant pH change.

Question 4

A buffer is made by mixing 0.10 mol of lactic acid ($$\mathrm{CH_3CH(OH)COOH}$$, $$K_a = 1.4 	imes 10$$^{-4}$$) and 0.10 mol of sodium lactate in 1.0 L of water. What is the pH of the buffer?

Accepted Answer

$$\mathrm{pH} = 3.85$$

Question 5

Which of the following best explains why the pH at the equivalence point of a weak acid–strong base titration is greater than 7?

Accepted Answer

The conjugate base of the weak acid hydrolyzes to produce OH– ions.

Question 6

Which indicator would be most suitable for the titration of a strong acid with a strong base?

Accepted Answer

An indicator with a color change interval around pH 7

Question 7

The solubility product constant ($$K_{sp}) $$for $$\mathrm{$$BaSO_4$$} is$$ $$1.1 	imes 10$$^{-10}$$. What is the molar solubility of $$\mathrm{$$BaSO_4$$}$$ in pure water?

Accepted Answer

$$1.0 	imes 10$$^{-5}$$~\mathrm{mol/L}$$

Question 8

What is the effect on the solubility of $$\mathrm{$$CaF_2$$}$$ when $$\mathrm{NaF} is $$added to the solution?

Accepted Answer

The solubility of $$\mathrm{$$CaF_2$$}$$ decreases due to the common-ion effect.

Question 9

A solution contains $$0.010~\mathrm{M}$$ $$\mathrm{Ca$$^{2+}$$}$$ and $$0.010~\mathrm{M}$$ $$\mathrm{F^-}. $$Will a precipitate of $$\mathrm{$$CaF_2$$}$$ form? ($$K_{sp}$$ for $$\mathrm{$$CaF_2$$} = 3.9 	imes 10$$^{-11}$$)

Accepted Answer

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

Question 10

Which of the following best describes the effect of adding ammonia ($$\mathrm{NH_3$}) to a $$solution containing $$\mathrm{AgCl}$$?

Accepted Answer

The solubility of $$\mathrm{AgCl}$$ increases due to the formation of $$\mathrm{[Ag(NH_3$)_2]^+}$$ complex ions.

Question 11

Which of the following is true about amphoteric oxides and hydroxides?

Accepted Answer

They are soluble in both strong acids and strong bases.

Question 12

A buffer is most effective when:

Accepted Answer

The pH is equal to the pKa of the acid.

Question 13

Which of the following steps is necessary to calculate the pH after adding a strong base to a buffer solution?

Accepted Answer

First, use stoichiometry to determine new concentrations, then apply the Henderson–Hasselbalch equation.

Question 14

Which of the following is the correct expression for the solubility product constant ($$K_{sp}) $$for $$\mathrm{Ba_3$(PO_4$)_2}$$?

Accepted Answer

$$K_{sp} = [\mathrm{Ba}^{2+}]^3[\mathrm{PO}_4$$^{3-}$$]^2$$

Question 15

During the titration of a polyprotic acid, what does the pH at the halfway point to the first equivalence point represent?

Accepted Answer

The pKa for the first dissociation

Question 16

Which of the following best explains why a buffer resists changes in pH upon addition of small amounts of acid or base?

Accepted Answer

The buffer contains both a weak acid and its conjugate base, which neutralize added H+ or OH–.

Question 17

Which of the following is a real-world application of selective precipitation?

Accepted Answer

Separating metal ions in qualitative analysis of unknown solutions

Additional Aspects of Aqueous Equilibria: Buffers, Titrations, and Solubility

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