CHE 162 Midterm #1 Conceptual Review

Kinetics 1.Ammonia gas (NH 3 ) is produced from hydrogen and nitrogen gas according to the following reaction: 3 H 2 (g) + N 2 (g) 2 NH 3 (g) If the rate of production of ammonia is R(NH 3 ), what is the rate of loss of hydrogen and nitrogen gas, respectively? a. R(NH 3 ); R(NH 3 )c. R(NH 3 ); R(NH 3 ) b. R(NH 3 ); 2 R(NH 3 )d. R(NH 3 ); 2 R(NH 3 )

Kinetics 1.Ammonia gas (NH 3 ) is produced from hydrogen and nitrogen gas according to the following reaction: 3 H 2 (g) + N 2 (g) 2 NH 3 (g) If the rate of production of ammonia is R(NH 3 ), what is the rate of loss of hydrogen and nitrogen gas, respectively? a. R(NH 3 ); R(NH 3 )c. R(NH 3 ); R(NH 3 ) b. R(NH 3 ); 2 R(NH 3 )d. R(NH 3 ); 2 R(NH 3 )

Kinetics 2.Which point on the following energy profile is the transition state?

Kinetics 2.Which point on the following energy profile is the transition state?

Kinetics 3.The following energy profiles for four different reactions are shown. Which of the reactions will have the largest rate constant? a.ac.c b.bd.d

Kinetics 3.The following energy profiles for four different reactions are shown. Which of the reactions will have the largest rate constant? a.ac.c b.bd.d

Kinetics 4.The following figure shows Arrhenius plots for four different reactions. Which reaction has the largest frequency factor?

Kinetics 4.The following figure shows Arrhenius plots for four different reactions. Which reaction has the largest frequency factor?

Kinetics 5.The mechanism for the reaction 2 H 2 O 2 (aq) 2 H 2 O() + O 2 (g) in the presence of I – (aq) is proposed to be Step 1: H 2 O 2 (aq) + I – (aq) ® H 2 O() + OI – (aq) (slow) Step 2: H 2 O 2 (aq) + OI – (aq) ® H 2 O() + O 2 (g) + I – (aq) (fast) What is the molecularity of the rate-determining step? a.unimolecular b.bimolecular c.termolecular d.Not enough information is presented to answer this question.

Kinetics 5.The mechanism for the reaction 2 H 2 O 2 (aq) 2 H 2 O() + O 2 (g) in the presence of I – (aq) is proposed to be Step 1: H 2 O 2 (aq) + I – (aq) ® H 2 O() + OI – (aq) (slow) Step 2: H 2 O 2 (aq) + OI – (aq) ® H 2 O() + O 2 (g) + I – (aq) (fast) What is the molecularity of the rate-determining step? a.unimolecular b.bimolecular c.termolecular d.Not enough information is presented to answer this question.

Kinetics 6.The following graph shows the kinetics curves for the reaction of nitrogen with hydrogen to form ammonia: N 2 (g) + 3H 2 (g) → 2 NH 3 (g). Which curve is hydrogen?

Kinetics 6.The following graph shows the kinetics curves for the reaction of nitrogen with hydrogen to form ammonia: N 2 (g) + 3H 2 (g) → 2 NH 3 (g). Which curve is hydrogen?

Kinetics The difference between an average rate and an instantaneous rate is 7. The difference between an average rate and an instantaneous rate is a. the average rate is taken over a larger time period. b. the instantaneous rate is taken from the slope of the curve at a specific time. c. they are not different if the time interval chosen is small enough. d. all the above are correct.

Kinetics The difference between an average rate and an instantaneous rate is 7. The difference between an average rate and an instantaneous rate is a. the average rate is taken over a larger time period. b. the instantaneous rate is taken from the slope of the curve at a specific time. c. they are not different if the time interval chosen is small enough. d. all the above are correct.

Kinetics 8.The rate of disappearance of HI in the reaction 2 HI(g) → I 2 (g) + H 2 (g) is shown in the following figure. What is the instantaneous rate of this reaction at t = 5 s?

Kinetics 8.The rate of disappearance of HI in the reaction 2 HI(g) → I 2 (g) + H 2 (g) is shown in the following figure. What is the instantaneous rate of this reaction at t = 5 s? Slope = rise run = M/S

Kinetics 9.Which of the following is not a possible graph of concentration vs. time for a reactant or a product?

Kinetics 9.Which of the following is not a possible graph of concentration vs. time for a reactant or a product?

Kinetics 10.The rates of chemical reactions a.are constant. b.decrease as the concentration of reactants decreases. c.decrease as the concentration of products increases. d.Both b and c are correct

Kinetics 10.The rates of chemical reactions a.are constant. b.decrease as the concentration of reactants decreases. c.decrease as the concentration of products increases. d.Both b and c are correct

Kinetics 11.The reaction 2 NO(g) + O2(g) → 2 NO2(g) has the following rate law: Rate = k[O2][NO] 2. If the concentration of NO is reduced by a factor of two, the rate will a.double. c. be reduced by 1/4 b.remain the same. d. be reduced by 1/2

Kinetics 11.The reaction 2 NO(g) + O2(g) → 2 NO2(g) has the following rate law: Rate = k[O2][NO] 2. If the concentration of NO is reduced by a factor of two, the rate will a.double. c. be reduced by 1/4 b.remain the same. d. be reduced by 1/2

Kinetics 12.What are the units of the rate constant for a first-order reaction a.M/s c. 1/Ms 2 b.1/Ms d. 1/s

Kinetics 12.What are the units of the rate constant for a first-order reaction a.M/s c. 1/Ms 2 b.1/Ms d. 1/s

Kinetics 13.Which of the following plots indicates that the reaction is zero order?

Kinetics 13.Which of the following plots indicates that the reaction is zero order?

Kinetics 14.Indicate which of the following plots would be obtained for a second-order reaction. c

Kinetics 14.Indicate which of the following plots would be obtained for a second-order reaction. c

Kinetics 15.Collision theory assumes that the rate of a reaction depends on a.the energy of collisions. b.the orientation of colliding molecules. c.the energy of collisions and the orientation of colliding molecules. d.the change in energy between the products and the reactants

Kinetics 15.Collision theory assumes that the rate of a reaction depends on a.the energy of collisions. b.the orientation of colliding molecules. c.the energy of collisions and the orientation of colliding molecules. d.the change in energy between the products and the reactants

Kinetics steps in a reaction mechanism are as follows. Which species is acting as a catalyst? Step 1: Ag + (aq) + Ce 4+ (aq) ↔ Tl 3+ (aq) + Ce 3+ (aq) Step 2: Tl + (aq) + Ag 2+ (aq) → Tl 2+ (aq) + Ag + (aq) Step 3: Tl 2+ (aq) + Ce 4+ (aq) → Tl 3+ (aq) + Ce 3+ (aq) 16.Consider the steps in the following mechanism. Which species is the catalyst.

Kinetics steps in a reaction mechanism are as follows. Which species is acting as a catalyst? Step 1: Ag + (aq) + Ce 4+ (aq) ↔ Tl 3+ (aq) + Ce 3+ (aq) Step 2: Tl + (aq) + Ag 2+ (aq) → Tl 2+ (aq) + Ag + (aq) Step 3: Tl 2+ (aq) + Ce 4+ (aq) → Tl 3+ (aq) + Ce 3+ (aq) 16.Consider the steps in the following mechanism. Which species is the catalyst.

Kinetics 17.The mechanism for the reaction 2 H 2 O 2 (aq) → 2 H 2 O(™) + O 2 (g) in the presence of I – (aq) is proposed to be Step 1: H 2 O 2 (aq) + I – (aq) → H 2 O(™) + OI – (aq) Step 2: H 2 O 2 (aq) + OI – (aq) → H 2 O(™) + O 2( g) + I – (aq) Which of the following species is an intermediate?

Kinetics 17.The mechanism for the reaction 2 H 2 O 2 (aq) → 2 H 2 O(™) + O 2 (g) in the presence of I – (aq) is proposed to be Step 1: H 2 O 2 (aq) + I – (aq) → H 2 O(™) + OI – (aq) Step 2: H 2 O 2 (aq) + OI – (aq) → H 2 O(™) + O 2( g) + I – (aq) Which of the following species is an intermediate?

Equilibrium 18.The law of mass action is a result of a. the law of conservation of matter. c. kinetics of reversible reactions. b. the law of conservation of energy. d. limiting reagent stoichiometry.

Equilibrium 18.The law of mass action is a result of a. the law of conservation of matter. c. kinetics of reversible reactions. b. the law of conservation of energy. d. limiting reagent stoichiometry.

Equilibrium 19.An equilibrium that strongly favors products has a. a value of K > 1. b. a value of K >> 1.d. a value of Q << 1.

Equilibrium 19.An equilibrium that strongly favors products has a. a value of K > 1. b. a value of K >> 1.d. a value of Q << 1.

Equilibrium 20.An increase in the number of moles of gas as the reaction goes from reactants to products in a gas-phase equilibrium results in a. K p > K c.c. K p = K c. b. K p < K c.d. K p + K c = (RT).

Equilibrium 20.An increase in the number of moles of gas as the reaction goes from reactants to products in a gas-phase equilibrium results in a. K p > K c.c. K p = K c. b. K p < K c.d. K p + K c = (RT).

Equilibrium 21.A sketch of the free energy for a hypothetical chemical equilibrium is shown here. What point on the axis representing the relative quantities of reactants and products corresponds to the equilibrium position? a.ac.c b.bd.d

Equilibrium 21.A sketch of the free energy for a hypothetical chemical equilibrium is shown here. What point on the axis representing the relative quantities of reactants and products corresponds to the equilibrium position? a.ac.c b.bd.d

Equilibrium 22.Which of the following is equivalent to increasing the value of Q? a. addition of reactantsc. removal of products b. addition of productsd. more than one of these

Equilibrium 22.Which of the following is equivalent to increasing the value of Q? a. addition of reactantsc. removal of products b. addition of productsd. more than one of these

Equilibrium 23.The equilibrium constant for the acid ionization of mercaptoethanol is 1.91 ´ 10 –10 : HSCH 2 CH 2 OH(aq) H + (aq) + SCH 2 CH 2 OH – (aq) A solution of mercaptoethanol in water a. is almost entirely ionized. c. is about one-half ionized. b. is almost entirely un-ionized. d. is a strong acid.

Equilibrium 23.The equilibrium constant for the acid ionization of mercaptoethanol is 1.91 ´ 10 –10 : HSCH 2 CH 2 OH(aq) H + (aq) + SCH 2 CH 2 OH – (aq) A solution of mercaptoethanol in water a. is almost entirely ionized. c. is about one-half ionized. b. is almost entirely un-ionized. d. is a strong acid.

Equilibrium 24.A chemical reaction that does not proceed fully to give all the products expected by stoichiometry is a.a dud. c. a half-reaction. b.at equilibrium. d. a semiquaver.

Equilibrium 24.A chemical reaction that does not proceed fully to give all the products expected by stoichiometry is a.a dud. c. a half-reaction. b.at equilibrium. d. a semiquaver.

Equilibrium 25.Since a catalyst promotes both the forward and reverse reactions in an equilibrium, what may be done to promote creation of products? a. removal of any reactants that are formed by the equilibrium b. lowering of the temperature to limit the reverse reaction progress c. removal of products as they are made d. all the above

Equilibrium 25.Since a catalyst promotes both the forward and reverse reactions in an equilibrium, what may be done to promote creation of products? a. removal of any reactants that are formed by the equilibrium b. lowering of the temperature to limit the reverse reaction progress c. removal of products as they are made d. all the above

Equilibrium 26.A chemical reaction that does not proceed fully to give all the products expected by stoichiometry is a.a dud. c. a half-reaction. b.at equilibrium. d. a semiquaver.

Equilibrium 26.A chemical reaction that does not proceed fully to give all the products expected by stoichiometry is a.a dud. c. a half-reaction. b.at equilibrium. d. a semiquaver.

Equilibrium 27.If the reaction quotient Q has a smaller value than the related equilibrium constant, K, a.the reaction will release heat to achieve equilibrium. b.the reaction is at equilibrium. c.the reaction will continue to make more products. d.the reaction will consume products and make reactants.

Equilibrium 27.If the reaction quotient Q has a smaller value than the related equilibrium constant, K, a.the reaction will release heat to achieve equilibrium. b.the reaction is at equilibrium. c.the reaction will continue to make more products. d.the reaction will consume products and make reactants.

Equilibrium 28.A chemical equilibrium may be established by a.starting a reaction with reactants only. b.starting a reaction with products only. c.starting a reaction with equal quantities of reactants and products. d.all the above.

Equilibrium 28.A chemical equilibrium may be established by a.starting a reaction with reactants only. b.starting a reaction with products only. c.starting a reaction with equal quantities of reactants and products. d.all the above.

Equilibrium 29.For a given chemical equilibrium, which of the following will not change the value of the equilibrium constant? a.the temperature of the equilibrium system b.the total concentration of all the reactants and products c.how the reaction is written d.the value of Q used to set up the reaction system

Equilibrium 29.For a given chemical equilibrium, which of the following will not change the value of the equilibrium constant? a.the temperature of the equilibrium system b.the total concentration of all the reactants and products c.how the reaction is written d.the value of Q used to set up the reaction system

Equilibrium 30.The equilibrium constant for an endothermic reaction a.increases with increasing temperature. b.decreases with increasing temperature. c.is temperature independent. d.cannot be predicted

Equilibrium 30.The equilibrium constant for an endothermic reaction a.increases with increasing temperature. b.decreases with increasing temperature. c.is temperature independent. d.cannot be predicted

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