Deck 13: When Reactants Turn Into Products

Question 1

Which of the following does not influence the speed of a chemical reaction?

A)concentration of the reactants
B)molecular mass of the reactants
C)surface area of solid reactants
D)temperature

Answer 1

molecular mass of the reactants

Question 2

Which of the following is not a term involved in determining the overall rate of a chemical reaction?

A)the total number of collisions per unit time
B)the total number of collisions in the gas phase
C)the fraction of collisions with energy greater than the activation energy
D)the fraction of collisions which occur with a favorable orientation

Answer 2

the total number of collisions in the gas phase

Question 3

Which of the following can be done to increase the likelihood that a chemical reaction will take place?

A)decrease the average speed of the reacting molecules
B)induce more collisions between reacting molecules
C)remove all the water from the reaction mixture
D)break the reaction up into a series of steps

Answer 3

induce more collisions between reacting molecules

Question 4

The rate of reaction: A (g)+ 3B (g)→ C (g)+ 2D (g)is Rate = -k[A][B]³. If the concentration of B is doubled while that of A is unchanged, the rate will ________.

A)stay the same
B)be increased by a factor of 6
C)double
D)be increased by a factor of 8

Question 5

The rate of a reaction is proportional to ________.

A)the total number of collisions that occur per unit time
B)the fraction of collisions with energy larger than the energy of activation
C)the fraction of collisions with the proper orientation
D)All of the above are correct.

Question 6

Which of the following is an exothermic reaction?

A)burning propane gas in a barbecue
B)burning gasoline when driving a car
C)creating an explosion by detonating nitroglycerine
D)All of the above are exothermic reactions.

Question 7

Consider the reaction X → Y with the following data: Energy of reactants = 50 kJ/mole;
Energy of reaction = -30 kJ/mole;
Energy of transition state = 90 kJ/mole.
The energy of products for the reaction is ________ kJ/mole.

A)-30
B)20
C)30
D)80

Question 8

In the diagram above, the two containers shown (Box A and BoxB)have exactly the same size (volume), are held at the same temperature, and contain reactant molecules (dots). In which box will the rate of reaction be faster?

A)Box A
B)Box B
C)The rate will be about the same in each box.
D)There is no way to tell which will be faster from this diagram.

Question 9

Which of the following statements regarding reaction mechanisms is true?

A)A mechanism is a series of steps whereby reactants are converted to products.
B)Reaction mechanisms must be determined experimentally.
C)Neither A nor B is true.
D)Both A and B are true.

Question 10

Which of the following does not affect the rate of a reaction?

A)the concentration of the reactants
B)the energy of activation
C)the temperature
D)the pressure

Question 11

Consider the reaction X → Y with the following data: Energy of reactants = 25 kJ/mole;
Energy of products = 75 kJ/mole;
Energy of transition state = 100 kJ/mole.
The energy of activation for the reverse reaction is ________ kJ/mole.

A)25
B)50.
C)75
D)100

Question 12

Which of the following is an endothermic reaction?

A)melting ice
B)freezing water
C)sublimation of dry ice
D)condensing water vapor

Question 13

Which statement is true about the reaction energy profile?

A)plots the relative energies of both the reactants and products
B)plots energy on the y-axis
C)traces the progress of the reaction on the x-axis
D)All of the above are true.

Question 14

Which of the following responses contains the two rate factors that comprise the rate constant (k)for a given chemical reaction?

A)the temperature and the number of collisions per unit volume
B)the number of collisions per unit volume and the fraction of collisions with a favorable orientation
C)the number of collisions with energy greater than the activation energy and the fraction of collisions with a favorable orientation
D)the number of collisions with energy greater than the activation energy and the temperature

Question 15

Consider the reaction C → D with the following data: Energy of reactants = 30 kJ/mole;
Energy of products = 20 kJ/mole;
Energy of transition state = 60 kJ/mole.
One can say with certainty that the reaction is ________ by ________kJ/mole and the energy of activation is ________ kJ/mole.

A)exothermic; 10; 30
B)endothermic; 10; 30
C)exothermic; 40; 30
D)endothermic; 40; 30

Question 16

The units for the rate of a reaction are ________.

A)concentration per unit of time
B)concentration multiplied by the unit of time
C)unit of time per unit of concentration
D)One cannot say with certainty since rate laws vary from reaction to reaction.

Question 17

Which of the following "adjustments" can be made to a chemical reaction system to increase the rate of reaction?

A)increase the reaction temperature
B)increase the concentrations of the reactants
C)add a catalyst
D)All of the above will increase the rate of reaction.
E)None of the above will increase the rate of reaction.

Question 18

In the diagram above, the containers shown (Box A and BoxB)contain exactly the same number of reactant molecules and are at the same temperature. In which box will the rate of reaction be faster?

A)Box A
B)Box B
C)Rate is about the same in each box.
D)No way to tell which is faster from this picture.

Question 19

Which of the following is an example of a substitution reaction?

A)CH₃CH₂OH + Br^- → CH₃CH₂Br + OH^-
B)2MnO₄^- + 5C₂O₄^2- + 16H⁺ → 10CO₂ + 2Mn²⁺ + 8H₂O
C)2Mg + O₂ → 2MgO
D)I₂ + H₂ → 2HI

Question 20

The fraction of collisions with the proper orientation depends on ________.

A)the strength of the bonds that are to be broken
B)the molecular shape of the molecule
C)the concentration
D)both A and B

Question 21

Consider the reaction A + B → Products. If the rate equation is Rate = -k[A]³[B]⁰ the order of the reaction with respect to A, B, and the total order respectively is ________.

A)3, 1, 1
B)3, 0, 2
C)3, 0, 3
D)3, 1, 4

Question 22

Which of the following may be considered as biochemical catalysts?

A)carbohydrates
B)DNA
C)enzymes
D)lipids

Question 23

If the kinetic energy of the reactant molecules is not high enough to overcome the activation energy barrier, ________.

A)the reverse reaction will occur
B)no reaction takes place
C)the reaction will occur anyway
D)the products will form at a slower rate

Question 24

In the following equation 2Y (g)→ Z (g)at 20 °C the following data were obtained: The rate law for this reaction is ________.

A)Rate = -k[Y]²
B)Rate = -k[Y]
C)Rate = -k[Y]⁰
D)Rate = -k[Y]^-1

Question 25

In the following equation 2 Y (g)+ X (g)→ Z (g)at 100 °C the following data were obtained: The rate law for this reaction is ________.

A)Rate = k[Y]²[X]
B)Rate = k[Y][X]²
C)Rate = k[Y][X]
D)Rate = k[Y]²[X]²

Question 26

The difference in energy between the reactants and products in a chemical reaction is called ________.

A)the heat of reaction
B)the activation energy
C)the energy of products
D)either B or C

Question 27

Which of the following statements is false?

A)The rate determining step is always the slowest step in a multistep mechanism.
B)The rate constant always changes with a variation in temperature.
C)The energy of activation controls the speed of reaction.
D)The rate of a reaction is independent of the concentration of reactants.

Question 28

In order for a chemical reaction to occur, ________.

A)the reactants must be in sufficient concentration
B)the products must be of lower energy than the reactants
C)the reactants must be of lower energy than the products
D)the reactants must possess sufficient energy to overcome the barrier of the activation energy

Question 29

In the following equation 2W (g)→ V (g)at 20 °C the following data were obtained: The rate law for this reaction is ________.

A)Rate = -k[W]²
B)Rate = -k[W]
C)Rate = -k[W]⁰
D)Rate = -k[W]^-1

Question 30

Which of the following is true about the activation energy?

A)It may increase by decreasing the temperature.
B)It may decrease by decreasing the temperature.
C)It may increase by increasing the concentration of reactants.
D)It is practically independent of both temperature and concentration of reactants.

Question 31

Which of the following is true about a catalyst?

A)It increases the rate of a reaction.
B)It lowers the energy of activation.
C)It is not used up in the process.
D)All of the above are true.

Question 32

The slow step in the multistep mechanism of a reaction ________.

A)controls the rate at which the products are formed
B)is the only step that involves the breaking of bonds
C)is equally significant in measuring the rate
D)is insignificant in the formation of products

Question 33

Consider the reaction A + B → C. Doubling the concentration of A leads to doubling the rate, while doubling the concentration of B quadruples the rate. The rate equation is, therefore, ________.

A)Rate = -k[A][B]²
B)Rate = -k[A]
C)Rate = - k[A]²
D)Rate = -k[A]²[B]

Question 34

A reaction follows the rate law: Rate = -k[A]²[B]¹. The overall order is ________.

A)-1
B)0
C)2
D)3

Question 35

The energy of activation may be affected by ________.

A)increasing the concentration of the reactants
B)higher temperature
C)decreasing the concentration of the reactants
D)the presence of a catalyst

Question 36

Generally in a biochemical reaction the first step involves ________.

A)the reaction of the enzyme with the active site of the substrate
B)the reaction of the substrate with the active site of the enzyme
C)the reaction of the substrate with the enzyme-substrate complex
D)the reaction of the enzyme with the enzyme-substrate complex

Question 37

Which of the following is not true when the temperature of the reaction mixture is decreased?

A)The average kinetic energy of both the reactant and product molecules is decreased.
B)The rate of the reaction is decreased.
C)The fraction of reactant molecules that have a low kinetic energies is increased.
D)The activation energy of the reaction is increased.

Question 38

The reaction A + B + C → Products follows the rate law: Rate = - k[A]¹[B]^-1[C]². The overall rate of this reaction is ________.

A)2
B)3
C)4
D)5

Question 39

A reaction follows the rate law: Rate = -k[A]³[B]^-1. The overall order is ________.

A)-1
B)0
C)2
D)3

Question 40

Which of the following is true about enzymes?

A)They speed up reactions in a selective fashion.
B)They are very large proteins.
C)They contain specifically shaped pockets that fit only specific reactant molecules.
D)All of the above are true.

Question 41

A catalyst lowers the activation energy for a chemical reaction.

Question 42

If the products have a higher energy than the reactants ________.

A)the reaction is exothermic
B)the reaction is endothermic
C)the reactants have less energy than the products
D)both B and C

Question 43

Given the reaction, 2A + B₂ → 2AB, which of the following factors could increase the reaction rate?
I. decreasing the temperature
II.adding a catalyst
III.increasing the surface area of solid reactants

A)I and II
B)II and III
C)I and III
D)II And III
E)III only

Question 44

An endothermic reaction usually leads to cooling.

Question 45

Adding a catalyst increases the rate of reaction by providing the additional energy needed to overcome a large energy of activation.

Question 46

For chemical reactions to occur at all, "old" bonds must be broken and "new" bonds must form.

Question 47

An exothermic reaction usually leads to a release in energy.

Question 48

For an exothermic reaction, the value for ΔE_rxn is a negative number.

Question 49

An exothermic reaction would feel cold.

Question 50

The rate constant of a reaction may be increased by ________.

A)increasing the concentration of reactants
B)increasing the temperature
C)adding a catalyst
D)all of the above

Question 51

The rate constant is dependant on the activation energy and reactant orientation.

Question 52

Knowing the mechanism of a reaction is advantageous because one may influence its rate to make the reaction useful.

Question 53

The reaction energy profile can tell if a reaction is exothermic or endothermic.

Question 54

It is possible to determine a given reaction's mechanism without performing any experiments of any kind.

Question 55

For an endothermic reaction, the value for ΔE_rxn is a negative number.

Question 56

The reaction: HCl + NaOH → H₂O + NaCl is a substitution reaction.

Question 57

In each of the following diagrams, the x-axis is the reaction coordinate and the y-axis is the potential energy. Which diagram corresponds to a reaction that has an activation energy of 35 kJ and an overall reaction energy of -110 kJ?

A)

B)

C)

D)

Question 58

Reaction rates can be varied by changing either the concentrations of the reacting species or the temperature at which the reaction is carried out.

Question 59

When the heat of reaction is a positive number, the reaction is exothermic.

Question 60

A lower energy of activation leads to more products favored in the reaction.

Question 61

The magnitude (size)of the energy of activation for the reverse reaction is exactly identical as it is for the forward reaction.

Question 62

Calculate a value for ΔE_rxn for a chemical reaction if the reactants have an energy of -400 kJ/mol and the products have an energy of +100 kJ/mol. Is this reaction exothermic or endothermic?

a)Estimate the value for the activation energy for this reaction.
b)Calculate ΔErxn.
c)Is this reaction exothermic or endothermic?

Question 63

The greater the concentration of the reactants, the greater the rate of the reaction.

Question 64

The value of E_a(reaction)is equal to the difference E_a(reactants)- E_a(products).

Question 65

Based on the collision theory, adding a catalyst to a reaction increases the reaction rate.

Question 66

When the products are higher in energy than the reactants, the reaction is endothermic.

Question 67

The reactants must collide with an energy ≥ the energy of activation for the reaction to occur.

Question 68

A high energy of activation leads to more products favored in the reaction.

Question 69

Based on the collision theory, decreasing temperature for a reaction increases the reaction rate.

Question 70

Calculate a value for ΔE_rxn for a chemical reaction, if the reactants have an energy of +300 kJ/mol and the products have an energy of +100 kJ/mol. Is this reaction exothermic or endothermic?

Question 72

The rate determining step is always the fastest step.

Question 73

A catalyst can be recovered at the end of the reaction.

Question 74

A catalyst need not be present in large quantities.

Question 75

Examine this reaction coordinate diagram and answer the questions that follow. a)Estimate the value for the activation energy for this reaction.
b)Calculate ΔE_rxn.
c)Is this reaction exothermic or endothermic?

Question 76

Industrial chemists often have their choice of catalysts to use when designing, for example, a factory that produces ammonia. Explain why biochemists studying life processes (such as protein metabolism)do not have the same variety of choices for which enzyme they would use.

Question 77

If the forward reaction is exothermic, the reverse is endothermic.

Question 78

Use the table below to answer the question that follows:
The above data were obtained in a kinetic study of the reaction.
a)Determine the orders x and y, assuming that rate = k[NO]^x[Cl₂]^y.
b)Determine the value for the rate constant, k, in Experiment 2.
c)Determine the overall order of this reaction.

Question 79

In the reaction where Rate = [A]², the rate is second order with respect to the reactant and second order overall.

Question 80

Match the rate of each reaction in the questions with the overall order that appears in the list below.