chem test 2

Under constant conditions, the half-life of a first-order reaction ________. A) is the time necessary for the reactant concentration to drop to half its original value B) is constant C) can be calculated from the reaction rate constant D) does not depend on the initial reactant concentration E) All of the above are correct.

All of the above are correct.

Which one of the following is not a valid expression for the rate of the reaction below? 4NH3 + 7O2 → 4NO2 + 6H2O

All of the above are valid expressions of the reaction rate.

The mechanism for formation of the product X is: A + B → C + D (slow) B + D → X (fast) The intermediate reactant in the reaction is ________. A) A B) B C) C D) D E) X

D

Which of the following is true? A) If we know that a reaction is an elementary reaction, then we know its rate law. B) The rate-determining step of a reaction is the rate of the fastest elementary step of its mechanism. C) Since intermediate compounds can be formed, the chemical equations for the elementary reactions in a multistep mechanism do not always have to add to give the chemical equation of the overall process. D) In a reaction mechanism, an intermediate is identical to an activated complex. E) All of the above statements are true.

If we know that a reaction is an elementary reaction, then we know its rate law.

Which one of the following is true concerning the Haber process? A) It is a process used for shifting equilibrium positions to the right for more economical chemical synthesis of a variety of substances. B) It is a process used for the synthesis of ammonia. C) It is another way of stating Le Châtelier's principle. D) It is an industrial synthesis of sodium chloride that was discovered by Karl Haber. E) It is a process for the synthesis of elemental chlorine.

It is a process used for the synthesis of ammonia

The rate law of a reaction is rate = k[D][X]. The units of the rate constant are ________. A) mol L-1s-1 B) L mol-1s-1 C) mol2 L-2s-1 D) mol L-1s-2 E) L2 mol-2s-1

L mol-1s-1

Which reaction will shift to the right in response to a decrease in volume? A) N2 (g) + 3H2 (g) 2NH3 (g) B) H2 (g) + Cl2 (g) 2 HCl (g) C) 2 SO3 (g) 2 SO2 (g) + O2 (g) D) 2HI (g) H2 (g) + I2 (g) E) 2 Fe2O3 (s) 4 Fe (s) + 3O2 (g)

N2 (g) + 3H2 (g) 2NH3 (g)

Based on Le Châtelier's principle, increasing pressure at constant temperature in the following reaction will not change the concentrations of reactants and products. A) N2O4 (g) 2NO2 (g) B) N2 (g) + O2 (g) 2NO (g) C) N2 (g) + 2O2 (g) 2NO2 (g) D) N2 (g) + 3H2 (g) 2NH3 (g) E) 2N2 (g) + O2 (g) 2N2O (g)

N2 (g) + O2 (g) 2NO (g)

Which of the following statements is true? A) Q does not change with temperature. B) Keq does not change with temperature, whereas Q is temperature dependent. C) K does not depend on the concentrations or partial pressures of reaction components. D) Q does not depend on the concentrations or partial pressures of reaction components. E) Q is the same as Keq when a reaction is at equilibrium

Q is the same as Keq when a reaction is at equilibrium.

How is the reaction quotient used to determine whether a system is at equilibrium? A) The reaction quotient must be satisfied for equilibrium to be achieved. B) At equilibrium, the reaction quotient is undefined. C) The reaction is at equilibrium when Q < Keq. D) The reaction is at equilibrium when Q > Keq. E) The reaction is at equilibrium when Q = Keq.

The reaction is at equilibrium when Q = Keq.

Which of the following expressions is the correct equilibrium-constant expression for the equilibrium between dinitrogen tetroxide and nitrogen dioxide? N2O4 (g) 2NO2 (g) A) [NO2]/N2O4] B) [NO2]^2/N2O4] C) [NO2]/N2O4]^2 D) [NO2][N2O4] E) [NO2]2[N2O4]

[NO2]^2/N2O4]

Consider the following reaction at equilibrium: 2NH3 (g) N2 (g) + 3H2 (g) Le Châtelier's principle predicts that the moles of in the reaction container will increase with ________. A) some removal of from the reaction vessel (V and T constant) B) a decrease in the total pressure (T constant) C) addition of some to the reaction vessel (V and T constant) D) a decrease in the total volume of the reaction vessel (T constant) E) an increase in total pressure by the addition of helium gas (V and T constant)

a decrease in the total pressure (T constant)

Which reaction will shift to the left in response to a decrease in volume? A) 2HI (g) H2 (g) + I2 (g) B) H2 (g) + Cl2 (g) 2 HCl (g) C) N2 (g) + 3H2 (g) 2 NH3 (g) D) 2 SO3 (g) 2 SO2 (g) + O2 (g) E) 4 Fe (s) + 3 O2 (g) 2 Fe2O3 (s)

) 2 SO3 (g) 2 SO2 (g) + O2 (g)

Consider the following reaction at equilibrium: 2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ Le Châtelier's principle predicts that a decrease in temperature will ________. A) decrease the partial pressure of O2 (g) B) increase the partial pressure of CO2 (g) C) decrease the value of the equilibrium constant D) increase the value of the equilibrium constant E) decrease the partial pressure of CO

) increase the value of the equilibrium constant

) The equilibrium constant for the gas phase reaction 2SO2 (g) + O2 (g) 2SO3 (g) is Keq = 2.80 × 102 at 999 K. At equilibrium, ________. A) products predominate B) reactants predominate C) roughly equal amounts of products and reactants are present D) only products are present E) only reactants are present

) products predominate

The equilibrium constant for the gas phase reaction 2NH3 (g) N2 (g) + 3H2 (g) is Keq = 230 at 300 °C. At equilibrium, ________. A) products predominate B) reactants predominate C) roughly equal amounts of products and reactants are present D) only products are present E) only reactants are present

) products predominate

The reaction 2NO2 → 2NO + O2 follows second-order kinetics. At 300 °C, [NO2] drops from 0.0100 M to 0.00650 M in 100.0 s. The rate constant for the reaction is ________ M-1s-1. A) 0.096 B) 0.65 C) 0.81 D) 1.2 E) 0.54

0.54

The following reaction is second order in [A] and the rate constant is 0.025 : A → B The concentration of A was 0.65 M at 33 s. The initial concentration of A was ________ M. A) 2.4 B) 0.27 C) 0.24 D) 1.4 E) 1.2 × 10-2

1.4

For the elementary reaction NO3 + CO → NO2 + CO2 the molecularity of the reaction is ________, and the rate law is A) 2, k[NO3][CO] B) 4, k[NO3][CO][NO2][CO2] C) 2, k[NO2][CO2] D) 2, k[NO3][CO]/[NO2][CO2] E) 4, k[NO2][CO2]/[NO3][CO]

2, k[NO3][CO]

The reaction CH3-N≡C → CH3-C≡N is a first-order reaction. At 230.3C, k=6.29x10^-4 If CH3--N---C is 1.00x10^-3 is 1.00 × 10-3 initially, is ________ M after A) 5.33 × 10-4 B) 2.34 × 10-4 C) 1.88 × 10-3 D) 4.27 × 10-3 E) 1.00 × 10-6

5.33 × 10-4

In the Arrhenius equation, k = Ae-Ea/RT ________ is the frequency factor. A) k B) A C) e D) Ea E) R

A

In the energy profile of a reaction, the species that exists at the maximum on the curve is called the ________. A) product B) activated complex C) activation energy D) enthalpy of reaction E) atomic state

activated complex

Of the following, ________ will lower the activation energy for a reaction. A) increasing the concentrations of reactants B) raising the temperature of the reaction C) adding a catalyst for the reaction D) removing products as the reaction proceeds E) increasing the pressure

adding a catalyst for the reaction

In which of the following reactions would increasing pressure at constant temperature change the concentrations of reactants and products, based on Le Châteliers principle? A) N2 (g) + 3H2 (g) 2NH3 (g) B) N2O4 (g) 2NO2 (g) C) N2 (g) + 2O2 (g) 2NO2 (g) D) 2N2 (g) + O2 (g) 2 O (g) E) all of the above

all of the above

The rate of a reaction depends on ________. A) collision frequency B) collision energy C) collision orientation D) all of the above E) none of the above

all of the above

) Consider the following reaction at equilibrium. 2CO2 (g) 2CO (g) + O2 (g) ΔH° = -514 kJ Le Châtelier's principle predicts that the equilibrium partial pressure of CO (g) can be maximized by carrying out the reaction ________. A) at high temperature and high pressure B) at high temperature and low pressure C) at low temperature and low pressure D) at low temperature and high pressure E) in the presence of solid carbon

at low temperature and low pressure

Which one of the following will change the value of an equilibrium constant? A) changing temperature B) adding other substances that do not react with any of the species involved in the equilibrium C) varying the initial concentrations of reactants D) varying the initial concentrations of products E) changing the volume of the reaction vessel

changing temperature

In general, as temperature goes up, reaction rate ________. A) goes up if the reaction is exothermic B) goes up if the reaction is endothermic C) goes up regardless of whether the reaction is exothermic or endothermic D) stays the same regardless of whether the reaction is exothermic or endothermic E) stays the same if the reaction is first order

goes up regardless of whether the reaction is exothermic or endothermic

The effect of a catalyst on an equilibrium is to ________. A) increase the rate of the forward reaction only B) increase the equilibrium constant so that products are favored C) slow the reverse reaction only D) increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture E) shift the equilibrium to the right

increase the rate at which equilibrium is achieved without changing the composition of the equilibrium mixture

A catalyst can ________ the rate of a reaction by providing an alternative pathway with a ________ activation energy A) decrease, higher B) increase, lower C) decrease, lower D) increase, higher E) decrease, constant

increase, lower

) The rate law of the overall reaction A + B → C is rate = k[A]2. Which of the following will not increase the rate of the reaction? A) increasing the concentration of reactant A B) increasing the concentration of reactant B C) increasing the temperature of the reaction D) adding a catalyst for the reaction E) All of these will increase the rate.

increasing the concentration of reactant B

The equilibrium constant for the gas phase reaction 2SO3 (g) 2SO2 (g) + O2 (g) is Keq = 3.6 × 10-3 at 999 K. At equilibrium, ________. A) products predominate B) reactants predominate C) roughly equal amounts of products and reactants are present D) only products are present E) only reactants are present

reactants predominate

The equilibrium constant for the gas phase reaction N2 (g) + 3H2 (g) 2NH3 (g) is Keq = 4.34 × 10-3 at 300 °C. At equilibrium, ________. A) products predominate B) reactants predominate C) roughly equal amounts of products and reactants are present D) only products are present E) only reactants are present

reactants predominate

The equilibrium-constant expression depends on the ________ of the reaction. A) stoichiometry B) mechanism C) stoichiometry and mechanism D) the quantities of reactants and products initially present E) temperature

stoichiometry

One difference between first- and second-order reactions is that ________. A) the half-life of a first-order reaction does not depend on [A]0; the half-life of a second-order reaction does depend on [A]0 B) the rate of both first-order and second-order reactions do not depend on reactant concentrations C) the rate of a first-order reaction depends on reactant concentrations; the rate of a second-order reaction does not depend on reactant concentrations D) a first-order reaction can be catalyzed; a second-order reaction cannot be catalyzed E) None of the above are true.

the half-life of a first-order reaction does not depend on [A]0; the half-life of a second-order reaction does depend on [A]0

At equilibrium, ________. A) all chemical reactions have ceased B) the rates of the forward and reverse reactions are equal C) the rate constants of the forward and reverse reactions are equal D) the value of the equilibrium constant is 1 E) the limiting reagent has been consumed

the rates of the forward and reverse reactions are equal