Chem II Test 2

Choose the correct statement about a container in which the chemical equilibrium is established: 2 SO2(g) + O2(g) 2 SO3(g) + heat

A decrease in the volume will decrease the amount of SO2 present

Which of the following statements is correct? A) A reaction rate cannot be calculated from the collision frequency alone. B) The number of collisions has no effect on the rate constant. C) A zero order reaction depends on the concentration of reactants. D) The activated complex is a chemical species that can be isolated and analysed. E) The orientation of a collision does not affect the rate constant. 4

A reaction rate cannot be calculated from the collision frequency alone

Choose the INCORRECT statement A) A reaction intermediate is produced and used up during the reaction. B) The rate-determining step is the slow-step. C) A transition state and a reaction intermediate are the same. D) A reaction intermediates have fully formed bonds. E) An activated complex has partially formed bonds

A transition state and a reaction intermediate are the same

Which statement is INCORRECT? A) If the forward reaction is endothermic, the reverse will be exothermic. B) An activated complex has higher energy than any molecule contributing to it. C) Activation energy is the same for forward and reverse reaction. D) In an endothermic reaction, activation energy is usually greater than the enthalpy. E) The activated complex will be the highest on the energy profile

Activation energy is the same for forward and reverse reaction

Choose the INCORRECT statement A) A bimolecular process is one involving a collision of two molecules. B) A reaction mechanism is a step-by-step detailed description of a chemical reaction. C) The rate-determining step is always the first step. D) An elementary process is a step in the mechanism. E) A unimolecular process is one in which a single molecule dissociates

An elementary process is a step in the mechanism

What is the main difference between a Pt catalyst and an enzyme catalyst?

An enzyme has greater substrate specificity

Define rate law

An experimentally determined equation that describes how the rate of reaction depends on the concentration of reactants

Choose the correct statement about the equilibrium: N2(g) + 3 H2(g) 2 NH3(g), Kp = 1 × 10-4 atm-2

Conducting the reaction under high pressures will increase the yield of ammonia

Which of the following is FALSE for a second order reaction? A) The slope of 1/[A]t versus time is k. B) t1/2 = 1/k[A]o. C) If 1/[A] versus time is a straight line, the reaction is second order. D) 1/[A]t - 1/[A]o = kt. E) Each successive half-life is 4 times as long as the previous

Each successive half-life is 4 times as long as the previous

Which of the following statements is INCORRECT? A) In gaseous reactions [A] can be expressed as concentration or as pressure. B) Half-life in a first order reaction is constant. C) For a first order reaction ln [A]t/[A]o = kt. D) In a zero order reaction the rate remains constant throughout the reaction. E) Radioactive decay is a first order reaction

For a first order reaction ln [A]t/[A]o = kt

If a catalyst is added to a reaction: I) the value of k is increased II) the value of k is decreased III) the rate is increased IV) the rate is decreased V) neither rate nor the constant are changed, only the order

I and III

A catalyst: I) lowers activation energy II) provides an alternate reaction pathway III) is consumed in the reaction and therefore does not appear in the chemical equation of each mechanism IV) speeds a reaction V) is heterogeneous if it is in a different phase than the reactants

I, II, IV, and V

Activation energy is: I) the minimum kinetic energy required for each molecule in a collision to produce a reaction. II) the minimum total kinetic energy required for the molecules in a collision to produce a reaction. III) a factor in determining the rate of a reaction. IV) high for fast reactions.

II and III

A factor that decreases the activation energy for a reaction: I) decreases the rate constant II) increases the rate constant III) has no effect on the rate constant IV) makes the product yield increase V) might be a catalyst

II and V

What will happen to the equilibrium in the reaction 2 A(g) B(g) + C(g), Kc = 1.25 at 300 K if a catalyst is added?

No change, catalyst only changes the rate

Which of the following situations involves a heterogeneous catalysis?

The catalyst is present in a different phase of matter than are the reactants and products

Which of the following statements is true about the reaction 2A-->B + C which is first order in A and first order overall?

The initial rate doubles with doubling of initial concentration of A

For the reaction: 3 Fe(s) + 4 H2O(g) Fe3O4(s) + 4 H2(g) what is the effect on equilibrium of increasing temperature of an exothermic reaction?

The reaction shifts to the left

For the reaction: 3 Fe(s) + 4 H2O(g) Fe3O4(s) + 4 H2(g) what is the effect of removing H2?

The reaction shifts to the right.

In the Arrhenius equation, ln k = -Ea/RT + ln A, the symbol A denotes

a constant that represents the frequency of collisions with the proper orientation and other steric conditions favorable for a reaction

Which of the following lowers the activation energy of a reaction? A) raising the temperature B) removing products C) adding reactants D) lowering the temperature E) adding a catalyst

adding a catalyst

According to the collision theory in gaseous molecules, collision frequency is ________ and reaction is ________ because ________.

high, relatively low, only a fraction of the collisions lead to a reaction

Which of the following keep the equilibrium position unchanged?

homogeneous catalyst

Consider the following chemical reaction at equilibrium: 2 Cl2(g) + 2 H2O(g) 4 HCl(g) + O2(g) This equilibrium can be shifted to the right by

increasing the volume of the mixture

A catalyst alters the rate of a chemical reaction by

inducing an alternate pathway for the reaction with generally lower activation energy

Activation energy

minimum kinetic energy that molecules must bring to their collisions for a chemical reaction to occur

If a reaction has a rate equation of rate = k[A][B][C] then it is

overall third order

The rate of a specific chemical reaction is independent of the concentrations of the reactants. Thus the reaction is

overall zero order

Which factor influences the value of the equilibrium constant for a reversible reaction?

raising the temperature

Equilibrium constant K is constant except when one varies the

temperature of the reaction

Define activation energy

the minimum total kinetic energy that molecules must bring to their collisions for a chemical reaction to occur

In a reaction at equilibrium involving only gases, a change in pressure of the reaction mixture shifts the position of equilibrium only when

the moles of gas are not equal on the two sides of the equation

If increasing the concentration of A in a chemical reaction causes no increase in the rate of the reaction, then we may say

the reaction rate is zero order in [A]

Which of the following has no effect on the rate of a reaction?

value of ̇H°

Choose the INCORRECT answer. The rate of a chemical reaction: A) may be increased by certain catalytic agents B) will be very rapid if the activation energy is large C) describes the change in concentration of a reactant or product with time D) usually is increased when the concentration of one of the reactants is increased E) is dependent on temperature

will be very rapid if the activation energy is large