Q: A solution contains 0.0144 M $$Ba^{2+}. $$What concentration of $$F^- is $$needed to initiate precipitation of $$BaF_2$$? ($$K_{sp} = 1.7 \times 10$$^{-6}$$)

$$[F^-] = 3.4 \times 10$$^{-2}$$ M

Question 1

Which of the following combinations will form a buffer solution?

Accepted Answer

0.10 M HNO2 and 0.10 M NaNO2

Question 2

A buffer solution is prepared by mixing 0.100 M acetic acid ($$HC_2H_3O_2) $$and 0.100 M sodium acetate ($$NaC_2H_3O_2). $$Which of the following best explains why the pH of this solution is resistant to change upon addition of a small amount of HCl?

Accepted Answer

The strong acid is neutralized by the conjugate base present in the buffer.

Question 3

Which equation correctly represents the neutralization reaction that occurs when NaOH is added to an acetic acid buffer?

Accepted Answer

$$NaOH_{(aq)} + HC_2H_3O_2_{(aq)} \rightarrow H_2O_{(l)} + NaC_2H_3O_2_{(aq)}$$

Question 4

A solution is made by mixing 0.200 M HF and 0.100 M HCl. Given $$K_a$$ for HF is $$6.8 	imes 10$$^{-4}$$, what is the percent ionization of HF in this solution?

Accepted Answer

0.67%

Question 5

Which of the following best describes the common-ion effect?

Accepted Answer

The addition of a strong electrolyte containing a common ion decreases the ionization of a weak electrolyte.

Question 6

Calculate the pH of a buffer solution that is 0.0500 M in benzoic acid ($$HC_7H_5O_2$$, $$K_a = 6.50 	imes 10$$^{-5}$$) and 0.150 M in sodium benzoate ($$NaC_7H_5O_2$$) at 25°C using the Henderson-Hasselbalch equation.

Accepted Answer

$$pH = 4.68$$

Question 7

Which of the following statements about buffer capacity is correct?

Accepted Answer

Buffer capacity increases with increasing absolute concentrations of buffer components.

Question 8

During the titration of a weak acid with a strong base, what is true at the half-neutralization point?

Accepted Answer

The pH equals the pKa of the weak acid.

Question 9

Which indicator would be most appropriate for detecting the equivalence point in the titration of a strong acid with a strong base?

Accepted Answer

Bromothymol blue (pH transition range 6.0–7.6)

Question 10

A solution contains 0.0144 M $$Ba^{2+}. $$What concentration of $$F^- is $$needed to initiate precipitation of $$BaF_2$$? ($$K_{sp} = 1.7 	imes 10$$^{-6}$$)

Accepted Answer

$$[F^-] = 3.4 	imes 10$$^{-2}$$ M

Question 11

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

Accepted Answer

Decreasing the pH

Question 12

A solution contains $$[Cu$$^{2+}$$] = 2 	imes 10$$^{-7}$$ M and $$[$$Zn^{2+}$$] = 3 	imes $$10^{-7} M. $$When $$S^{2-} is $$added, which salt will precipitate first? ($$K_{sp,CuS} = 6 	imes 10$$^{-37}$$, K$$_{sp,ZnS} = 2 	imes $$10^{-25})$$

Accepted Answer

CuS

Question 13

Which of the following best describes an amphoteric hydroxide?

Accepted Answer

A hydroxide that is soluble in both acidic and basic solutions

Question 14

Which of the following is the correct expression for the solubility product constant ($$K_{sp}) $$for $$Ca_3$$($$PO_4)_2$?

Accepted Answer

$$K_{sp} = [Ca$$^{2+}$$]^3 [PO_4$^{3-}]^2$$

Question 15

Which of the following statements about complex ion formation is correct?

Accepted Answer

The formation of a complex ion increases the solubility of a metal salt.

Question 16

A buffer solution is most effective when:

Accepted Answer

The concentrations of acid and base are equal.

Question 17

Which of the following best explains why the addition of NaCl to a saturated solution of PbCl$$_2$$ decreases the solubility of PbCl$$_2$$?

Accepted Answer

The common ion (Cl$$^-) $$shifts the equilibrium to the left, decreasing solubility.

Question 18

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

Accepted Answer

The pH at the equivalence point is greater than 7.

Question 19

Which of the following best describes selective precipitation?

Accepted Answer

A process in which a reagent is added to precipitate one ion while leaving others in solution.

Aqueous Ionic Equilibrium: Buffers, Titrations, and Solubility

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