Q: A saturated solution of silver chloride ($$\ce{AgCl}) $$has a solubility product constant $$K_{sp} = 1.8 \times 10$$^{-10}$$ at 25$$^\circ\mathrm{C}$$. What is the molar solubility of $$\ce{AgCl}$$ in pure water?

$$s = \sqrt{1.8 \times 10$$^{-10}$$} = 1.34 \times 10$$^{-5}$$\ \mathrm{mol/L}$$

Question 1

A chemical system at equilibrium is disturbed by increasing the concentration of one of the reactants. According to Le Chatelier's Principle, what will happen to the system?

Accepted Answer

The system will shift to the right, favoring the formation of more products.

Question 2

The equilibrium constant $$K_c$$ for the reaction $$\ce{Fe$$^{3+}$$ + SCN^-  $$FeSCN^{2+}$$} is $$measured in a laboratory experiment. If the initial concentrations are $$[\ce{Fe$$^{3+}$$}] = 0.0020\ \mathrm{M}$$, $$[\ce{SCN^-}] = 0.0020\ \mathrm{M}$$, and $$[\ce{$$FeSCN^{2+}$$}] = 0$$, and at equilibrium $$[\ce{$$FeSCN^{2+}$$}] = 0.0015\ \mathrm{M}$$, what is the value of $$K_c$$?

Accepted Answer

$$K_c = \dfrac{[\ce{$$FeSCN^{2+}$$}]}{[\ce{Fe$$^{3+}$$}][\ce{SCN^-}]} = \dfrac{0.0015}{(0.0020-0.0015)(0.0020-0.0015)} = 600$$

Question 3

A solution is prepared by mixing $$0.10\ \mathrm{mol} of $$acetic acid ($$\ce{CH3COOH}) $$and $$0.10\ \mathrm{mol} of $$sodium acetate ($$\ce{CH3COONa}) in $$enough water to make $$1.0\ \mathrm{L} of $$solution. The $$K_a of $$acetic acid is $$1.8 	imes 10$$^{-5}$$. What is the pH of the buffer solution?

Accepted Answer

$$\mathrm{pH} = \mathrm{p}K_a + \log \left( \dfrac{[\ce{A^-}]}{[\ce{HA}]} \right) = 4.74 + \log(1) = 4.74$$

Question 4

Which of the following salts will produce a basic solution when dissolved in water?

Accepted Answer

Sodium acetate ($$\ce{CH3COONa})$$

Question 5

A $$25.0\ \mathrm{mL}$$ sample of $$0.100\ \mathrm{M}$$ hydrochloric acid is titrated with $$0.100\ \mathrm{M}$$ sodium hydroxide. What is the pH at the equivalence point?

Accepted Answer

7.00

Question 6

Which of the following best describes a buffer solution?

Accepted Answer

A solution that resists changes in pH when small amounts of acid or base are added.

Question 7

A saturated solution of silver chloride ($$\ce{AgCl}) $$has a solubility product constant $$K_{sp} = 1.8 	imes 10$$^{-10}$$ at 25$$^\circ\mathrm{C}$$. What is the molar solubility of $$\ce{AgCl}$$ in pure water?

Accepted Answer

$$s = \sqrt{1.8 	imes 10$$^{-10}$$} = 1.34 	imes 10$$^{-5}$$\ \mathrm{mol/L}$$

Question 8

Which of the following statements about the entropy ($$\Delta S) of a $$system is correct?

Accepted Answer

Entropy increases when a solid melts to form a liquid.

Question 9

Consider the following redox reaction: $$\ce{Zn(s) + Cu$$^{2+}$$(aq) -\u003e Zn$$^{2+}$$(aq) + Cu(s)}. $$Which species is oxidized and which is reduced?

Accepted Answer

Zn is oxidized; Cu$$^{2+} is $$reduced.

Question 10

A voltaic cell is constructed using a zinc electrode in $$1.0\ \mathrm{M}\ \ce{ZnSO4}$$ and a copper electrode in $$1.0\ \mathrm{M}\ \ce{CuSO4}. $$The standard reduction potentials are $$E^\circ_{\ce{Zn$$^{2+}$$/Zn}} = -0.76\ \mathrm{V}$$ and $$E^\circ_{\ce{Cu$$^{2+}$$/Cu}} = +0.34\ \mathrm{V}. $$What is the standard cell potential ($$E^\circ_{cell}$$)?

Accepted Answer

$$E^\circ_{cell} = E^\circ_{cathode} - E^\circ_{anode} = 0.34\ \mathrm{V} - (-0.76\ \mathrm{V}) = 1.10\ \mathrm{V}$$

Question 11

Which of the following best explains why adding a common ion decreases the solubility of a sparingly soluble salt?

Accepted Answer

The addition of a common ion shifts the dissolution equilibrium to the left, decreasing solubility.

Question 12

A diprotic acid $$\ce{H2A} is $$titrated with $$\ce{NaOH}. $$Which of the following statements is true about the titration curve?

Accepted Answer

There are two equivalence points, each corresponding to the neutralization of one proton.

Question 13

Which of the following is the correct net ionic equation for the precipitation of barium sulfate when solutions of $$\ce{BaCl2}$$ and $$\ce{Na2SO4}$$ are mixed?

Accepted Answer

$$\ce{Ba$$^{2+}$$(aq) + SO4$$^{2-}$$(aq) -\u003e BaSO4(s)}$$

Question 14

Which of the following coordination compounds will exhibit geometric (cis-trans) isomerism?

Accepted Answer

$$\ce{[Pt(NH3)_2Cl_2]}$$

Question 15

Which of the following statements about nuclear reactions is correct?

Accepted Answer

Nuclear reactions involve changes in the nucleus and can result in the transformation of one element into another.

Question 16

A spontaneous reaction at constant temperature and pressure must have which of the following?

Accepted Answer

$$\Delta G \u003c 0$$

Question 17

Which of the following best describes the function of a salt bridge in a voltaic cell?

Accepted Answer

It allows the flow of ions to maintain electrical neutrality in the half-cells.

Question 18

A sample of $$\ce{Ba(IO3)_2} is $$dissolved in water and the solubility is measured. If the $$K_{sp}$$ for $$\ce{Ba(IO3)_2} is$$ $$6.0 	imes 10$$^{-10}$$, what is the molar solubility (s$) of $$\ce{Ba(IO3)_2}$$ in pure water?

Accepted Answer

$$K_{sp} = [\ce{Ba$$^{2+}$$}][\ce{IO3^-}]^2 = s 	imes (2s)^2$ = 4s^3$ \implies s = \sqrt[3]{\dfrac{K_{sp}}{4}} = \sqrt[3]{\dfrac{6.0 	imes 10$$^{-10}$$}{4}} = 5.0 	imes 10$$^{-4}$$\ \mathrm{mol/L}$$

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