Deck 6: Energy Changes,reaction Rates,and Equilibrium

Question 1

Which value (if any)in each pair corresponds to a faster reaction?

A)E_a = 1 kcal
B)E_a = 10 kcal
C)E_a = 100 kcal
D)Reaction rate is independent of E_a value.

Answer 1

E_a = 1 kcal

Question 2

Which value (if any)in each pair corresponds to a slower reaction?

A)E_a = 1 kcal
B)E_a = 10 kcal
C)E_a = 100 kcal
D)Reaction rate is independent of E_a value.

Answer 2

E_a = 100 kcal

Question 3

A chemical reaction requires 31.39 kJ. How many kilocalories does this correspond to?

A)7,502 kcal
B)7.502 kcal
C)131.3 kcal
D)0.1313 kcal
E)31.39 kcal

Answer 3

7.502 kcal

Question 4

Consider the reaction,3 NO₂(g)+ H₂O(l)→ 2 HNO₃(aq)+ NO(g),where ΔH = -137 kJ. How many kilojoules are released when 92.3 g of NO₂ reacts?

A)2.01 kJ are released
B)2.75 × 10² kJ are released
C)91.6 kJ are released
D)1.26 × 10⁴ kJ are released

Question 5

Consider the reaction,C₂H₄(g)+ H₂(g)→ C₂H₆(g),where ΔH = -137 kJ. How many kilojoules are released when 55.3 g of C₂H₄ reacts?

A)137 kJ are released
B)270. kJ are released
C)1.13 × 10³ kJ are released
D)7.58 × 10³ kJ are released

Question 6

Which of the following energy quantities is equivalent to 258 Cal?

A)258 cal
B)1080 J
C)1080 kJ
D)6.17 × 10⁴ kJ

Question 7

Which quantity represents the largest amount of stored energy?

A)10 grams of fat
B)10 grams of carbohydrate
C)10 grams of protein
D)5 grams of carbohydrate plus 5 grams of protein
E)5 grams of protein plus 5 grams of fat

Question 8

Consider the reaction,C₂H₄(g)+ H₂(g)→ C₂H₆(g),where ΔH = -137 kJ. How many kilojoules are released when 3.5 mol of C₂H₄ reacts?

A)137 kJ are released
B)570 kJ are released
C)480 kJ are released
D)2.0 × 10³ kJ are released

Question 9

Which term correctly describes a reaction in which the energy of the products is higher than the energy of the reactants?

A)Oxidation-reduction
B)Endothermic
C)Exothermic
D)Combustion

Question 10

In the reaction: 2 C₂H₆(g)+ 7 O₂(g)→ 4 CO₂(g)+ 6 H₂O(g),increasing the concentration of C₂H₆(g)will ________.

A)increase the activation energy of the reaction
B)decrease the activation energy of the reaction
C)decrease the ΔH of the reaction
D)increase the reaction rate
E)decrease the reaction rate

Question 11

Which of the following energy quantities is equivalent to 11.9 kcal?

A)1.19 × 10⁵ cal
B)49.8 J
C)49.8 kJ
D)2.84 × 10³ kJ

Question 12

The law of conservation of energy states that ________.

A)the energy of the reactants and products in a chemical reaction are always equal
B)all chemical reactions are reversible
C)energy can be created,but not destroyed
D)energy cannot be created or destroyed

Question 13

A peanut butter and jelly sandwich contains 9.00 g of fat,6.00 g of protein,and 25.0 g of carbohydrate. How many Calories does this sandwich provide?

A)205 Cal
B)360 Cal
C)160 Cal
D)260 Cal
E)190 Cal

Question 14

Consider the reaction: C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g),where ΔH = -531 kcal. Which statement concerning this reaction is true?

A)Heat is absorbed.
B)The bonds formed in the products are stronger than the bonds broken in the reactants.
C)The products are higher in energy than the reactants.
D)The reaction is endothermic.

Question 15

Which bond is the weakest?

A)H-Br
B)H-Cl
C)H-F
D)H-I

Question 16

Which of the following is a true statement about the energy diagram shown below?

A)A labels the E_a of the reaction and B labels ΔH of the reaction.
B)A labels the ΔH of the reaction and B labels E_a of the reaction.
C)C labels the activation energy.
D)D labels the reactants and E labels the products.

Question 17

A chemical reaction releases 55.2 kcal. How many kilojoules does this correspond to?

A)231 kJ
B)0.231 kJ
C)13.2 kJ
D)1,320 kJ

Question 18

Which of the following energy quantities is equivalent to 578 J?

A)5.78 × 10⁵ kJ
B)138 kcal
C)0.138 kcal
D)1.38 × 10⁵ kcal

Question 19

Which bond is the strongest?

A)H-Br
B)H-Cl
C)H-F
D)H-I

Question 20

Catalysts accelerate a reaction by ________.

A)lowering the enthalpy of the reaction
B)lowering the energy of activation
C)raising the enthalpy of the reaction
D)raising the energy of activation

Question 21

Which statement about catalysts is NOT true?

A)A catalyst increases the rate of a chemical reaction.
B)A catalyst lowers the activation energy of a chemical reaction.
C)A catalyst lowers the ΔH of a chemical reaction.
D)A catalyst is recovered unchanged in the reaction it catalyzes.

Question 22

An equilibrium constant with a value of 1.5 × 10^-9 indicates that at equilibrium ________.

A)the reactants are favored
B)the products are favored
C)approximately equal concentrations of reactants and products are present
D)there are more products present than reactants

Question 23

What is the expression for the equilibrium constant for the reaction: 2 C₂H₆(g)+ 7 O₂(g) 4 CO₂(g)+ 6 H₂O(g)?

A)
B)
C)
D)

Question 24

Consider the combustion reaction of propane: C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g),where ΔH = -531 kcal. If 1.24 × 10⁵ kcal of energy is released in the reaction,how many moles of propane were burned?

A)234 mol of C₃H₈
B)6.58 × 10⁷ mol of C₃H₈
C)0.00428 mol of C₃H₈
D)0.0179 mol of C₃H₈

Question 25

Consider the reversible reaction at equilibrium: N₂(g)+ O₂(g) 2 NO(g). What is the effect of removing some N₂(g)from the equilibrium system?

A)The concentration of O₂(g)increases
B)The concentration of O₂(g)decreases
C)The concentration of NO(g)increases
D)The equilibrium system shifts to the right

Question 26

The reversible reaction: PCl₃(g)+ Cl₂(g) PCl₅(g),has K = 0.5. Based on the molecular art shown below,what can be inferred about the reaction conditions?

A)The reaction has not yet reached equilibrium.
B)The reaction mixture is at equilibrium.
C)The reaction will shift to the left to reach equilibrium.
D)The forward reaction is favorable.

Question 27

An equilibrium constant with a value of 8.0 × 10⁶ indicates that at equilibrium ________.

A)the reactants are favored
B)the products are favored
C)approximately equal concentrations of reactants and products are present
D)there are more reactants present than products

Question 28

For an endothermic reaction at equilibrium,increasing the temperature ________.

A)does not shift the equilibrium since K is a constant
B)increases the rate of the reverse reaction to form more reactants
C)increases the rate of the forward reaction to form more products
D)increases the rate of the reverse reaction to form more products

Question 29

Consider the reaction: N₂(g)+ O₂(g) 2 NO(g). If [N₂] = 0.520 M,[O₂] = 0.0662 M,and [NO] = 0.00956 at equilibrium,what is the value of K?

A)3.60
B)0.278
C)377
D)0.00265

Question 30

When the pressure of a reaction at equilibrium decreases,in which direction does the equilibrium shift?

A)The equilibrium shifts in the direction that increases the number of moles of gas.
B)The equilibrium shifts in the direction that decreases the number of moles of gas.
C)The equilibrium does not shift.
D)The equilibrium shifts always shifts to the right.
E)The equilibrium shifts always shifts to the left.

Question 31

A catalytic converter uses a catalyst to catalyze three reactions that clean up the exhaust from an auto engine. Which element is not used as a catalyst in catalytic converters?

A)Platinum
B)Rhodium
C)Sulfur
D)Palladium

Question 32

Consider the combustion reaction of propane: C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g),where ΔH = -531 kcal. If 6.70 × 10⁴ kcal of energy is released in the reaction,how many grams of oxygen were consumed?

A)63.1 g of O₂
B)2.02 × 10⁴ g of O₂
C)12.6 g of O₂
D)404 g of O₂

Question 33

Walking at a brisk pace burns off about 280 Cal/h. How long would you have to walk to burn off the Calories obtained from eating a candy bar that contained 3 g of protein,12 g of fat,and 28 g of carbohydrates?

A)55 minutes
B)230 minutes
C)50 minutes
D)210 minutes

Question 34

Consider the reaction: C₃H₈(g)+ 5 O₂(g)→ 3 CO₂(g)+ 4 H₂O(g),where ΔH = -531 kcal/mol. How much heat is released when 3.40 × 10²⁰ molecules of C₃H₈(g)is burned?

A)3.33 kcal
B)0.300 kcal
C)6.40 × 10¹⁷ kcal
D)1.50 kcal

Question 35

Which K value below is consistent with an equilibrium system in which the products are favored?

A)K = 1
B)K = 5.2 x 10⁴
C)K = 3.8 x 10^-6
D)K = 0.100

Question 36

What is the gas phase chemical reaction that corresponds to the equilibrium constant expression shown below?

A)2 A + 4 B 2 C
B)A + B C
C)2 C 2 A + 4 B
D)2 C 4 A + 2 B
E)4 A + 2 B 2 C

Question 37

Which of the following will increase the rate of a reaction?

A)Increasing the temperature
B)Increasing the concentration of a reactant
C)Adding a catalyst
D)Ensuring that the reactants are properly aligned when they collide
E)All of these changes will increase the rate of a reaction.

Question 38

Consider the reaction: PCl₃(g)+ Cl₂(g) PCl₅(g). If [PCl₃] = 0.78 M,[Cl₂] = 0.44 M,and [PCl₅] = 0.88 at equilibrium,what is the value of K?

A)0.39
B)1.4
C)2.6
D)0.72

Question 39

Which K value below is consistent with an equilibrium system in which the reactants are favored?

A)K = 1
B)K = 1.8 x 10³
C)K = 3.7 x 10^-8
D)K = 500

Question 40

The molecular art depicts the following reversible reaction at equilibrium: CO(g)+ Cl₂(g) COCl₂(g). What can be inferred about the equilibrium constant,K,for this reaction?

A)K < 1
B)K ~ 1
C)K > 1
D)K = 0

Question 41

A reversible reaction has reached equilibrium when which condition is established?

A)the reverse reaction begins to occur
B)the concentrations of reactants and products become equal
C)all of the reactants have been converted into products
D)the forward and reverse reaction rates become equal

Question 42

Bond breaking is endothermic.

Question 43

Exothermic reactions involve the formation of products having lower energy than the reactants.

Question 44

The difference in energy between the reactants and the transition state is called the energy of activation,symbolized by E_a.

Question 45

The hydrolysis of sucrose depicted below has K = 1.4 × 10⁵. Which of the following is a reasonable assumption about this reaction once equilibrium is established? sucrose + H₂O glucose + fructose

A)The equilibrium mixture contains equal amounts of sucrose,glucose,and fructose.
B)The equilibrium mixture contains mostly glucose and fructose.
C)The equilibrium mixture contains mostly sucrose.
D)The equilibrium shifts to the left due to the high value for K.

Question 46

Reactions with high E_a are generally fast reactions.

Question 47

Breaking a chemical bond requires energy.

Question 48

The rate of a chemical reaction increases with an increase in the concentration of one or more reactants. This is best explained by which statement?

A)The higher concentration of reactants increases the potential energy of the molecules.
B)The higher concentration of reactants increases the activation energy of the reaction.
C)The higher concentration of reactants increases the temperature of the molecules.
D)The higher concentration of reactants increases the frequency of collisions between molecules.

Question 49

Bond dissociation energies are always positive numbers.

Question 50

Ammonia (NH₃)is synthesized by the reaction of nitrogen and hydrogen in the presence of an iron catalyst according to the equation below. Removing the iron catalyst would decrease the reaction rate.

Question 51

An endothermic reaction is one in which energy is absorbed and ΔH is negative (-).

Question 52

Which statement concerning the reversible reaction 2 NO₂(g) N₂O₄(g)is true?

A)NO₂ is the product of the forward reaction.
B)The reverse reaction produces N₂O₄.
C)At the start of the reaction,the forward and reverse reaction rates are equal.
D)As the forward reaction progresses and more N₂O₄ is formed,the reverse reaction rate increases.

Question 53

The energy of the reacting molecules affects whether a particular collision will lead to a chemical reaction.

Question 54

The stronger the bond,the higher its bond dissociation energy.

Question 55

Energy is the capacity to do work.

Question 56

The rusting of iron is described by the reaction: 4 Fe(s)+ 3 O₂(g)→ 2 Fe₂O₃(s). The formation of rust on an exposed piece of iron typically takes several months. Which of the following is NOT a reasonable assumption about this chemical reaction?

A)The formation of rust has a low reaction rate.
B)The formation of rust has a low activation energy.
C)The formation of rust would occur more slowly at higher altitudes where the concentration of oxygen is lower.
D)The formation of rust would occur faster in the warmer summer months than in the cooler winter months.

Question 57

Which of the following is NOT a reasonable assumption about the chemical reaction whose energy diagram is depicted below?

A)The activation energy for the reaction is 100kJ.
B)The reaction is exothermic.
C)ΔH= -25kJ
D)The reaction is favorable.

Question 58

One step in the metabolism of glucose is depicted below. Which statement best describes how the equilibrium system would respond if the amount of dihydroxyacetone phosphate is decreased?

A)The system would shift to the left,consuming more dihydroxyacetone phosphate.
B)The system would shift to the right,producing more dihydroxyacetone phosphate and glyceraldehyde 3-phosphate.
C)The system would shift to the left,producing more fructose 1,6-bisphosphate.
D)The system would shift to the right,consuming some glyceraldehyde 3-phosphate and producing more dihydroxyacetone phosphate.

Question 59

Which of the following is ALWAYS necessary for a chemical reaction to occur between two reactants,A and B?

A)Equal amounts of A and B must be present
B)A and B must be present in the same physical state
C)The reaction must be carried out at a temperature higher than room temperature
D)A and B must collide with the proper orientation and with a certain minimum amount of energy

Question 60

Changes in potential energy occur in chemical reactions.

Question 61

Consider the following reversible reaction at equilibrium: CO(g)+ Cl₂(g) COCl₂(g). If chlorine gas is added to the reaction vessel,the concentration of carbon monoxide will decrease.

Question 62

Consider the following reversible reaction at equilibrium: C­₆­H₁₂O₆ (aq)+ 6 O₂(g) 6 CO₂(g)+ 6 H₂O(l). If carbon dioxide gas is removed from the reaction vessel,the equilibrium will shift to the right.

Question 63

Increasing the concentration of the reactants in a chemical reaction increases the number of collisions,and the reaction rate increases.

Question 64

Consider the following reversible reaction at equilibrium: 2 NO(g)+ O₂(g) 2 NO₂(g). If the pressure inside the reaction vessel is increased,the equilibrium will shift to the right.

Question 65

In the energy diagram shown below,the ΔH of the reaction is labeled by D.

Question 66

When the equilibrium constant for a reaction is much less than one (K < 1),the concentration of the products is larger than the concentration of the reactants.

Question 67

Increasing the temperature of a reaction mixture usually results in a decrease in the reaction rate.

Question 68

Chemical reactions are considered favorable if the products have a higher energy than the reactants.

Question 69

Once equilibrium is reached in a chemical reaction,reactants stop forming products.

Question 70

A reversible reaction in which K = 9.65 × 10^-14 contains a negligible amount of reactants at equilibrium.

Question 71

Consider the following reversible reaction at equilibrium: 2 NO(g)+ O₂(g) 2 NO₂(g). If oxygen gas is added to the reaction vessel,the equilibrium will shift to the left.

Question 72

The expression for the equilibrium constant,K,for the general reaction: a A + b B c C + d D is .

Question 73

Activation energy is the minimum amount of energy necessary for a reaction to occur.

Question 74

Enzymes are proteins that act as biological catalysts.

Question 75

Consider the following reversible reaction at equilibrium: CO(g)+ Cl₂(g) COCl₂(g). If the pressure inside the reaction vessel is increased,the equilibrium will shift to the left.

Question 76

Consider the following reversible reaction at equilibrium: CO(g)+ Cl₂(g) COCl₂(g),where ΔH = -108.6 kJ. When the temperature of the reaction vessel decreases,the system responds by forming more COCl₂.

Question 77

Le Châtelier's principle is a general rule used to explain the effect of a change in reaction conditions on equilibrium.

Question 78

Consider the following reversible reaction at equilibrium: CO(g)+ Cl₂(g) COCl₂(g). If chlorine gas is added to the reaction vessel,the equilibrium will shift to the right.

Question 79

Consider the following reversible reaction at equilibrium: C­_6­H₁₂O₆ (aq)+ 6 O₂(g) 6 CO₂(g)+ 6 H₂O(l). If oxygen gas is removed from the reaction vessel,the equilibrium will shift to the right.

Question 80

The larger the K for a reaction,the faster the reaction.