Question 1

A reaction with an activation energy of 123 kJ/mol has a rate constant of 0.200 s$$^{-1} at 38$^	ext{o}C. At $$what temperature will the rate constant be 0.400 s$$^{-1}$$? Use the Arrhenius equation: $$k = A e$$^{-E_a/(RT)}$$.

Accepted Answer

43$$^	ext{o}C$$

Question 2

The rate constant of a second-order reaction is $$3.86 	imes 10$$^{-2}$$ M$$^{-1}$$s$$^{-1}$$. If the concentration of reactant A is 0.160 M after 75.6 s, what was the initial concentration, $$[A]_0$$? Use the integrated rate law for second-order reactions: $$\frac{1}{[A]} = \frac{1}{[A]_0} + kt$$.

Accepted Answer

0.300 M

Question 3

A nonelectrolyte with empirical formula C$$_3H$_9Al is $$dissolved in benzene, raising the boiling point from 80.10$$^	ext{o}C to 80.35$^	ext{o}C. If 0.144 g of $$the compound is dissolved in 10.0 g benzene and $$K_b = 2.53$$ $$^	ext{o}C/$$molal, what is the molecular formula of the compound? Use $$\Delta T_b = K_b m.$$

Accepted Answer

C$$_9H$_{27}Al$_3$$

Question 4

What is the concentration of a $$1.570 	imes 10$$^{-6}$$ M aqueous solution of AgNO_3$ expressed in parts-per-million (ppm)? Assume a density of 1.00 g/mL. (Molar mass of AgNO_3$ = 169.88 g/mol)

Accepted Answer

1.57 ppm

Question 5

In the collision model, which factor is most sensitive to changes in temperature?

Accepted Answer

The fraction of molecules with energy greater than the activation energy.

Question 6

Which solute would be the least soluble in the given solvent?

Accepted Answer

Na$$_2CO$_3 in C$_6H$_{12}$$

Question 7

Taking ion-pairing into account, which of the following solutions should have the smallest freezing point depression ($$\Delta T_f$$)?

Accepted Answer

0.10 m MgSO$$_4$$

Question 8

A student obtains the following plots from data collected in lab. Which rate law below is the most likely for the reaction?

Accepted Answer

rate = k[A]

Question 9

The balanced equation for the reaction of iodide ion with H$$_3$$AsO$$_4 in $$acidic solution is: $$3	ext{I}^- + 	ext{H}_3	ext{AsO}_4 + 2	ext{H}^+ ightarrow 	ext{I}_3^- + 	ext{H}_3	ext{AsO}_3 + 	ext{H}_2	ext{O}. If$$ $$-\Delta[	ext{I}^-]/\Delta t = 6.2 	imes 10$$^{-3}$$ M/s, what is $$-\Delta[	ext{H}^+]/\Delta t$$?

Accepted Answer

4.1 	imes $$10^{-3}$ M/s

Question 10

The reaction A$$_2 ightarrow B + C $$obeys the rate law: $$	ext{rate} = (1.0 	imes 10$$^{-2}$$ 	ext{ min}^{-1}) [A_2$] at 298 K. $$How long will it take for the reaction to reach 60% completion? Use the first-order integrated rate law: $$\ln([A]_0/[A]) = kt.$$

Accepted Answer

3.9 min

Question 11

Using the data table for the reaction between hemoglobin (Hb) and carbon monoxide (CO), determine the rate constant for the reaction. Assume the rate law is $$	ext{rate} = k[	ext{Hb}][	ext{CO}].$$

Accepted Answer

0.280 L/μmol•s

Question 12

For a particular ionic substance, $$\Delta H_{	ext{soln}} is +22 kJ/$$mol and $$\Delta H_{	ext{mix}} is -629 kJ/$$mol. Estimate the magnitude of the lattice energy for the substance. (Disregard the enthalpy required to separate the water molecules.) Use $$\Delta H_{	ext{soln}} = U_{	ext{lattice}} + \Delta H_{	ext{mix}}.$$

Accepted Answer

651 kJ/mol

Question 13

For the energy profiles shown, which statement is true?

Accepted Answer

Reaction Z has 1 intermediate and 2 transition states.

Question 14

If 31 grams of K$$_2Cr$_2O$_7 is $$placed in 50.0 grams of water at 50$$^	ext{o}C$$, what is the molality of the resulting solution? (Molar mass of K$$_2Cr$_2O$_7 = 294.185 g/$$mol, MM of water = 18 g/mol)

Accepted Answer

2.1 m

Question 15

The rate of disappearance of O$$_2$$ was measured and the following data was collected: [O$$_2$$] (M) at t = 0.0 s: 2.30, t = 30.0 s: 1.65, t = 60.0 s: 1.23, t = 90.0 s: 1.01, t = 120.0 s: 0.95. Which time range has the greatest average rate?

Accepted Answer

t = 0.0 s to t = 30.0 s

Question 16

For the reaction: 2 ClO$$_2(g) + 2 OH$^-(aq$$) $$\rightarrow$$ ClO$$_3^- (aq) + $$ClO$$_2^- (aq) + H$_2O(l$$), the following kinetic data were obtained at 298 K: Experiment 1: [ClO$$_2$$] = 0.0600 M, [OH$$^-$$] = 0.0300 M, Initial Rate = 0.0248 M/sec; Experiment 2: [ClO$$_2$$] = 0.0200 M, [OH$$^-$$] = 0.0300 M, Initial Rate = 0.00827 M/sec; Experiment 3: [ClO$$_2$$] = 0.0200 M, [OH$$^-$$] = 0.0900 M, Initial Rate = 0.0247 M/sec. Calculate the rate constant $$k$$ for this reaction at 298 K.

Accepted Answer

12.7 M$$^{-2} s$^{-1}$$

Question 17

What is the mole fraction of naphthalene in a 1.92 m solution of naphthalene (C$$_{10}H$_8) $$dissolved in toluene (C$$_7H$_8$$)? (MW of C$$_{10}H$_8= 128.17 g/$$mol; C$$_7H$_8 = 92.14 g/$$mol)

Accepted Answer

0.150

Question 18

The boiling point of acetone is 56.00$$^	ext{o}C. 3.75 g of $$CaCl$$_2$$ was dissolved in 121 mL of acetone. What is the boiling point of the solution? (MW: acetone = 58.08 g/mol; CaCl$$_2 = 110.98 g/$$mol, $$K_b = 1.67$$ $$^	ext{o}C/m$$, density of acetone = 0.784 g/mL)

Accepted Answer

56.09

Question 19

What is the mole fraction of heptane (C$$_7H$_{16}) in $$the vapor phase of a solution of 0.226 mol CBr$$_4$$ and 0.271 mol C$$_7H$_{16} at 100$^	ext{o}C$$? (Vapor pressures of pure substances at 100$$^	ext{o}C$$: CBr$$_4 = 47.2 $$torr; C$$_7H$_{16} = 493.19 $$torr)

Accepted Answer

0.859

Question 20

Which of the following solutes would be the least soluble in the given solvent?

Accepted Answer

NaCl in CCl$$_4$$

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