Q: A saturated solution of $$\mathrm{$$CaF_2$$}$$ has a molar solubility of $$2.1 \times 10$$^{-4}$$\ \mathrm{mol/L}. $$What is the value of $$K_{sp}$$ for $$\mathrm{$$CaF_2$$}$$?

$$K_{sp} = (2.1 \times 10$$^{-4}$$)(2 \times 2.1 \times 10$$^{-4}$$)^2 = (2.1$$ \times $$10^{-4})(4.2$$ \times $$10^{-4})^2$

Question 1

Which of the following is the correct Ksp expression for the dissolution of $$\mathrm{AgCl(s)} in $$water?

Accepted Answer

$$K_{sp} = [\mathrm{Ag^+}][\mathrm{Cl^-}]$$

Question 2

A saturated solution of $$\mathrm{$$CaF_2$$}$$ has a molar solubility of $$2.1 	imes 10$$^{-4}$$\ \mathrm{mol/L}. $$What is the value of $$K_{sp}$$ for $$\mathrm{$$CaF_2$$}$$?

Accepted Answer

$$K_{sp} = (2.1 	imes 10$$^{-4}$$)(2 	imes 2.1 	imes 10$$^{-4}$$)^2 = (2.1$$ 	imes $$10^{-4})(4.2$$ 	imes $$10^{-4})^2$

Question 3

Which of the following will decrease the solubility of $$\mathrm{AgCl} in $$water?

Accepted Answer

Adding $$\mathrm{HCl}$$

Question 4

How does decreasing the pH affect the solubility of $$\mathrm{$$CaCO_3$$}$$?

Accepted Answer

It increases the solubility

Question 5

Which of the following best explains why $$\mathrm{AgCl} is $$more soluble in the presence of $$\mathrm{NH_3$}$$?

Accepted Answer

$$\mathrm{NH_3$}$$ forms a complex ion with $$\mathrm{Ag^+}$$

Question 6

Which pair of salts will precipitate first when $$\mathrm{NaCl} is $$added to a solution containing $$\mathrm{Ag^+}$$ and $$\mathrm{Pb$$^{2+}$$}$$ ions, given $$K_{sp}(\mathrm{AgCl}) = 1.8 	imes 10$$^{-10}$$ and K$$_{sp}(\mathrm{$$PbCl_2$$}) = 1.7 	imes $$10^{-5}$$?

Accepted Answer

$$\mathrm{AgCl}$$ will precipitate first

Question 7

Which of the following processes is thermodynamically spontaneous at room temperature?

Accepted Answer

Ice melting at $$25^\circC$$

Question 8

Which statement best describes entropy ($$S$$)?

Accepted Answer

Entropy measures the degree of randomness or disorder of a system

Question 9

Which of the following reactions would have a positive entropy change ($$\Delta S \u003e 0$$)?

Accepted Answer

$$\mathrm{H_2O(l) \rightarrow H_2O(g)}$$

Question 10

Given $$\Delta H = -100\ \mathrm{kJ}$$ and $$\Delta S = -200\ \mathrm{J/K}$$, at what temperature does the reaction change from spontaneous to nonspontaneous?

Accepted Answer

$$T = 500\ \mathrm{K}$$

Question 11

Which of the following is the correct relationship between Gibbs free energy and equilibrium constant?

Accepted Answer

$$\Delta G = -RT \ln K$$

Question 12

Which of the following is the correct cell reaction for a galvanic cell made from $$\mathrm{Zn}$$ and $$\mathrm{Cu}$$ electrodes?

Accepted Answer

$$\mathrm{Cu$$^{2+}$$ + Zn \rightarrow Zn$$^{2+}$$ + Cu}$$

Question 13

What is the oxidation number of sulfur in $$\mathrm{H_2SO_4}$$?

Accepted Answer

+6

Question 14

Which species is reduced in the following reaction: $$\mathrm{2Fe$$^{3+}$$ + 2I^- \rightarrow 2Fe$$^{2+}$$ + I_2$}$$?

Accepted Answer

$$\mathrm{Fe$$^{3+}$$}$$

Question 15

Which of the following half-reactions occurs at the cathode in a standard electrochemical cell?

Accepted Answer

$$\mathrm{Cu$$^{2+}$$ + 2e^- \rightarrow Cu}$$

Question 16

If the standard reduction potentials are $$E^\circ(\mathrm{Ag^+/Ag}) = +0.80\ \mathrm{V}$$ and $$E^\circ(\mathrm{Cu$$^{2+}$$/Cu}) = +0.34\ \mathrm{V}$$, which metal will be reduced at the cathode in a cell containing both ions?

Accepted Answer

$$\mathrm{Ag}$$

Question 17

Which of the following statements about entropy is correct?

Accepted Answer

A gas has higher entropy than a liquid

Question 18

Which of the following is true for a reaction at equilibrium?

Accepted Answer

$$\Delta G = 0$$

Question 19

Which of the following best describes the effect of a common ion on the solubility of an ionic compound?

Accepted Answer

It decreases the solubility

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