Chemistry: Molecular Nature of Matter and Change, 6th Edition (Silberberg)

Chapter 16: Kinetics: Rates and Mechanisms of Chemical Reactions

Self-Assessment Quiz 2

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1			Consider the reaction: CH3Cl(aq) + OH-(aq) → CH3OH(aq) + Cl-(aq) If the rate of appearance of CH3OH(aq) remains constant at 1.0 x 10-4 mol/(L·min), and the initial concentrations of both reactants are 0.10 mol/L, how long will it take to consume half of the reactants?
			A)	10,000 min
			B)	1,000 min
			C)	500 min
			D)	100 min
			E)	none of the above
2			Consider the reaction 2A + 2B + C → 2D + E If the rate law for this reaction is Rate = k[A][B]2, what will be the effect on the rate if the concentrations of A, B and C are all doubled at the same time?
			A)	The rate will increase by a factor of 2.
			B)	The rate will increase by a factor of 4.
			C)	The rate will increase by a factor of 6.
			D)	The rate will increase by a factor of 8.
			E)	More information is needed before this question can be answered.
3			Nitric oxide (NO) reacts with hydrogen (H2) according to the equation: 2NO(g) + 2H2(g) → N2(g) + 2H2O(g) The following initial rates of reaction have been measured for the given reactant concentrations. <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0310402656/38225/Image56.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (5.0K)</a> Which of the following is the rate law (rate equation) for this reaction?
			A)	rate = k[NO]2 [H2]
			B)	rate = k[NO] [H2]2
			C)	rate = k[NO] [H2]4
			D)	rate = k[NO] [H2]
			E)	rate = k[NO]1/2 [H2]1/4
4			The following initial rate data were collected for the reaction: 2A + B → C + D <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0310402656/38225/Image57.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (5.0K)</a> What is the value of the rate constant?
			A)	k = 1.42 x 10-2 s-1
			B)	k = 2.83 x 10-3 L mol-1 s-1
			C)	k = 1.42 L2 mol-2 s-1
			D)	k = 0.532 x 10-3 L2 mol-2 s-1
			E)	k = 4.26 x 10-1 L mol-1 s-1
5			A solution of sucrose in water has an initial concentration of 0.155 mol/L. The sucrose is being converted to other sugars in a reaction which is first-order with respect to the sucrose concentration. Exactly 30 minutes later, the sucrose concentration has fallen to 0.131 mol/L. Calculate the value of the rate constant in s-1.
			A)	9.3 x 10-5 s-1
			B)	4.1 x 10-5 s-1
			C)	5.6 x 10-3 s-1
			D)	1.7 x 10-1 s-1
			E)	none of the above
6			The reaction A → products is first-order with respect to A. Which of the following correctly describes a plot of rate data for this reaction?
			A)	[A] plotted vs time gives a straight line of negative slope.
			B)	[A] plotted vs time gives a straight line of positive slope.
			C)	ln[A] plotted vs time gives a straight line of positive slope.
			D)	ln[A] plotted vs time gives a straight line of negative slope.
			E)	1/[A] plotted vs time gives a straight line of positive slope.
7			Tetrafluoroethene (C2F4) dimerizes at 300º C to form octafluorocyclobutane (cyclo-C4F8) according to the equation 2C2F4(g) → cyclo-C4F8(g) The rate law for the reaction is: Rate = (0.080 L mol-1 min-1)[C2F4]2 In an experiment where the initial concentration of tetrafluoroethylene is 0.10 mol/L, what concentration remains after 700 min?
			A)	8.0 X 10-3 mol/L
			B)	8.0 X 10-4 mol/L
			C)	2.8 X 10-3 mol/L
			D)	0.075 mol/L
			E)	0.015 mol/L
8			For the reaction A → products, the rate law is Rate = k[A]2. Starting with [A] = 0.100 mol/L, its concentration is found to be 0.0652 mol/L after 600. seconds. What is the value of the rate constant?
			A)	5.8 x 10-5 L . mol-1 .s-1
			B)	7.1 x 10-4 L . mol-1 .s-1
			C)	3.2 x 10-3 L . mol-1 .s-1
			D)	8.9 x 10-3 L . mol-1 .s-1
			E)	none of the above
9			In an enzymatic fermentation, the initial concentration of sugar is 0.16 mol/L; after 10.0 hours the concentration is 0.080 mol/L; after 20.0 hours the concentration is 0.040 mol/L. What is the order of this reaction, and what is the rate constant?
			A)	zero order; 1.67 x 10-6 s-1
			B)	first order; 1.93 x 10-5 s-1
			C)	first order; 1.67 x 10-6 s-1
			D)	second order; 3.71 x 10-10 s-1
			E)	second order; 1.67 x 10-6 s-1
10			From the following data, estimate the activation energy for the gas-phase reaction H2 + I2 → 2HI <a onClick="window.open('/olcweb/cgi/pluginpop.cgi?it=gif::::/sites/dl/free/0310402656/38225/Image58.gif','popWin', 'width=NaN,height=NaN,resizable,scrollbars');" href="#"><img valign="absmiddle" height="16" width="16" border="0" src="/olcweb/styles/shared/linkicons/image.gif"> (2.0K)</a>
			A)	21.0 kJ/mol
			B)	2.10 x 104 kJ/mol
			C)	1.75 x 102 kJ/mol
			D)	9.00 x 102 kJ/mol
			E)	none of the above
11			A second-order rate constant is given by k = (6.5 x 107 L·mol-1·s-1)e-13500 K/T What is the the activation energy, Ea, for this reaction?
			A)	135 kJ/mol
			B)	56 kJ/mol
			C)	112 kJ/mol
			D)	162 kJ/mol
			E)	782 kJ/mol
12			The reaction of ethylene (C2H4) with butadiene (C4H6) to form cyclohexene (C6H10) has an activation energy (Ea) of 115 kJ/mol. The reverse reaction (decomposition of cyclohexene to ethylene and butadiene) has an activation energy of 287 kJ/mol. What is the heat of reaction, Δ Hrxn, for the forward reaction?
			A)	+115 kJ/mol
			B)	+287 kJ/mol
			C)	-287 kJ/mol
			D)	+172 kJ/mol
			E)	-172 kJ/mol
13			Consider the following mechanism for the oxidation of bromide ions by hydrogen peroxide in aqueous acid solution. (1) H+ + H2O2 → H3O2+ (rapid equilibrium) (2) H3O2+ + Br- → HOBr + H2O (slow) (3) HOBr + H+ + Br- → Br2 + H2O (fast) What is the overall reaction equation for this process?
			A)	2H+ + H2O2 + Br- + HOBr → H3O2+ + Br2 + H2O
			B)	H3O2+ + H+ + 2Br- → Br2 + 2H2O
			C)	2H+ + 2Br- + H2O2 → Br2 + 2H2O
			D)	2H3O2+ + 2Br- → H2O2 + Br2 + 2H2O
			E)	none of the above
14			The mechanism for the gas-phase reaction 2NO + Cl2 → 2NOCl is suggested to be: (1) NO + NO → N2O4 (slow) (2) N2O4 + Cl2 → 2NOCl (fast) Based on this mechanism, the rate law for the overall reaction is:
			A)	Rate = k [NO]
			B)	Rate = k [NO]2
			C)	Rate = k [NO2]2[Cl2]
			D)	Rate = k [Cl2]
			E)	Rate = k [NO2]2[Cl2]2
15			At elevated temperatures in the gas phase, cyclopropane reacts to form propene. The rate of reaction is given by: rate = Δ[propene]/Δt = k[cyclopropane]. Which one of the following actions is least likely to cause a change in the rate of this reaction?
			A)	adding a catalyst
			B)	raising the temperature
			C)	doubling the initial amount of cyclopropane
			D)	halving the volume of the reaction vessel, but keeping the initial amount of cyclopropane constant.
			E)	continuously removing propene as it is formed

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