Q: For the reaction $$\mathrm{CH_3COCH_2}(aq) + \mathrm{HOCl}(aq) \rightarrow \mathrm{CH_3COCH_2Cl}(aq) + \mathrm{H_2O}(l)$$, which is catalyzed by OH$$^-$$ and is first order in $$[\mathrm{CH_3COCH_2}]$$, first order in $$[\mathrm{OH}^-]$$, and zero order in $$[\mathrm{HOCl}]$$, what is the correct rate law?

$$\text{Rate} = k[\mathrm{CH_3COCH_2}][\mathrm{OH}^-]$$

Q: Which of the following is the correct formula for calculating the standard enthalpy change of a reaction ($$\Delta H_{rxn}^\circ) $$using standard enthalpies of formation?

$$\Delta H_{rxn}^\circ = \sum \Delta H_f^\circ(\text{products}) - \sum \Delta H_f^\circ(\text{reactants})$$

Question 1

Which of the following correctly represents the balanced formation reaction for sodium chromate dihydrate ($$\mathrm{Na_2CrO_4 \cdot 2H_2O}) $$from its elements in their standard states?

Accepted Answer

$$2\mathrm{Na}(s) + \mathrm{Cr}(s) + 2\mathrm{O}_2(g) + 2\mathrm{H}_2O(l) \rightarrow \mathrm{Na_2CrO_4 \cdot 2H_2O}(s)$$

Question 2

Given the reaction $$2\mathrm{CrOCl}(s) + 2\mathrm{NaCl}(s) + \mathrm{H_2O}(l) \rightarrow 2\mathrm{NaClO}(s) + \mathrm{HClO}(aq) + \mathrm{Cr_2O_3}(s)$$ with $$\Delta H_{rxn} = -340.2\ \mathrm{kJ}$$, what is the sign and magnitude of the enthalpy change for the reaction?

Accepted Answer

Negative, $$340.2\ \mathrm{kJ}$$

Question 3

A mixture of 50.0 L of He(g) and Ne(g) at 25°C and 1.00 atm has a partial pressure of He of 0.87 atm. What is the mass of the mixture? ($$M_{He} = 4.00\ \mathrm{g/mol}$$, $$M_{Ne} = 20.18\ \mathrm{g/mol}$$, $$R = 0.0821\ \mathrm{L\cdot atm\cdot $$mol^{-1}$$\cdot K$$^{-1}$$})$$

Accepted Answer

$$22.6\ \mathrm{g}$$

Question 4

For the reaction $$\mathrm{CH_3COCH_2}(aq) + \mathrm{HOCl}(aq) \rightarrow \mathrm{CH_3COCH_2Cl}(aq) + \mathrm{H_2O}(l)$$, which is catalyzed by OH$$^-$$ and is first order in $$[\mathrm{CH_3COCH_2}]$$, first order in $$[\mathrm{OH}^-]$$, and zero order in $$[\mathrm{HOCl}]$$, what is the correct rate law?

Accepted Answer

$$	ext{Rate} = k[\mathrm{CH_3COCH_2}][\mathrm{OH}^-]$$

Question 5

If the initial concentrations of $$\mathrm{CH_3COCH_2}$$ and $$\mathrm{HOCl}$$ are increased by a factor of 2.5 and $$[\mathrm{OH}^-]$$ remains unchanged, by what factor will the initial rate of the reaction increase?

Accepted Answer

2.5

Question 6

The following reaction is first order in $$\mathrm{N_2O_5}$$ and its rate constant is $$3.46 	imes 10$$^{-3}$$\ \mathrm{s}^{-1} at 20$$°C: $$2\mathrm{N_2O_5}(g) ightarrow 4\mathrm{NO_2$}(g) + \mathrm{O_2$}(g). $$What time in minutes would it take for the reaction to consume 99% of the initial amount of $$\mathrm{N_2O_5}$$?

Accepted Answer

1,330 s

Question 7

For the reaction $$A \rightarrow C$$ via two steps, which of the following statements is true if the rate-determining step is the one with the largest activation energy?

Accepted Answer

The step with the largest activation energy has the smallest rate constant.

Question 8

Consider the reversible reaction $$\mathrm{$$HSO_4$$^-}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{SO_4$^{2-}}(aq) + \mathrm{H_3O^+}(aq)$$ with $$\Delta H_{rxn} \u003e 0. $$What will happen to the equilibrium position if the temperature is increased?

Accepted Answer

Shift to the right

Question 9

Which of the following is the correct expression for the equilibrium constant $$K$$ for the reaction $$\mathrm{$$HSO_4$$^-}(aq) + \mathrm{H_2O}(l) \rightleftharpoons \mathrm{SO_4$^{2-}}(aq) + \mathrm{H_3O^+}(aq)$$?

Accepted Answer

$$K = \dfrac{[\mathrm{SO_4$^{2-}}][\mathrm{H_3O^+}]}{[\mathrm{$$HSO_4$$^-}]}$$

Question 10

Which of the following pairs correctly identifies the conjugate acid-base pair in the reaction $$\mathrm{NH_4$^+}(aq) + \mathrm{Na_2HPO_4}(aq) \rightarrow \mathrm{NH_3$}(aq) + \mathrm{Na_2H_2PO_4}(aq)$$?

Accepted Answer

$$\mathrm{NH_4$^+}$$ / $$\mathrm{NH_3$}$$

Question 11

Which of the following is the correct balanced net ionic equation for the acid-base reaction between $$\mathrm{NH_4$^+}(aq)$$ and $$\mathrm{$$HPO_4$$^{2-}}(aq)$$?

Accepted Answer

$$\mathrm{NH_4$^+}(aq) + \mathrm{$$HPO_4$$^{2-}}(aq) \rightarrow \mathrm{NH_3$}(aq) + \mathrm{H_2PO_4^-}(aq)$$

Question 12

Rank the following acids in order of increasing $$K_a$$ value: $$\mathrm{$$HSO_4$$^-}$$, $$\mathrm{H_2SO_4}$$, $$\mathrm{$$HClO_4$$}$$, $$\mathrm{H_3PO_4}.$$

Accepted Answer

$$\mathrm{H_3PO_4} \u003c \mathrm{$$HSO_4$$^-} \u003c \mathrm{H_2SO_4} \u003c \mathrm{$$HClO_4$$}$$

Question 13

Which of the following solutions has the highest entropy of vaporization, assuming ideal conditions?

Accepted Answer

$$\mathrm{CH_3OH}$$

Question 14

Calculate the pH of a 0.050 M solution of HBr(aq) ($$pK_a($$HBr) = -9) at 25°C.

Accepted Answer

1.30

Question 15

What is the pH of a 0.40 M solution of a monoprotic acid HA(aq) ($$pK_a(HA) = 7.77) at 25$$°C?

Accepted Answer

3.89

Question 16

Which of the following equations correctly relates the rate constant $$k to $$activation energy $$E_a$$ and temperature $$T$$ according to the Arrhenius equation?

Accepted Answer

$$k = A e$$^{-E_a/(RT)}$$

Question 17

Which of the following is the correct formula for calculating the standard enthalpy change of a reaction ($$\Delta H_{rxn}^\circ) $$using standard enthalpies of formation?

Accepted Answer

$$\Delta H_{rxn}^\circ = \sum \Delta H_f^\circ(	ext{products}) - \sum \Delta H_f^\circ(	ext{reactants})$$

Question 18

Which of the following statements about the effect of a catalyst on a chemical reaction is correct?

Accepted Answer

A catalyst lowers the activation energy, increasing the rate of reaction without affecting the equilibrium position.

General Chemistry III: Thermochemistry, Kinetics, Equilibrium, and Acid-Base Chemistry – Study Notes

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