Chem chapter 7

Calculate the enthalpy for the combustion of propane shown using the given bond dissociation energies: C3H8 + 5 O2 3 CO2 + 4H2O Number and types of bonds in each molecule: C3H8 (2 C-C, 8 C-H bonds); O2 (1 O=O); (2 C=O bonds); (2 O-H bonds). Bond dissociation energies: C-C (347 kJ/mol); C-H (413 kJ/mol); O=O (498 kJ/mol; C=O (799 kJ/mol); O-H (467 kJ/mol)

-2042 kJ

How much heat is released during the combustion of methane using the given bond dissociation energies: CH4 + 2 O2 CO2 + 2H2O Number and types of bonds in each molecule: CH4 (4 C-H bonds); O2 (1 O=O); (2 C=O bonds); (2 O-H bonds). Bond dissociation energies: C-C (347 kJ/mol); C-H (413 kJ/mol); O=O (498 kJ/mol; C=O (799 kJ/mol); O-H (467 kJ/mol)

-8181 kJ

Consider the reaction shown: P4(s) + 10 Cl2(g) 4 PCl5(s) + 452 kcal When 50.00 g of P4 react, ________ kcal will be ________.

182.4; produced

Consider the reaction shown: 304.0 kcal + 4 PCl3(l) P4(s) + 6 Cl2(g) When 50.00 g of PCl3 react, ________ kcal will be ________.

27.67; consumed

Calculate the equilibrium constant for the reaction below if a tank was found to contain 0.106 M O2, 0.00652 M SO3 , and 0.00129 M SO2. 2 SO3(g) 2 SO2(g) + O2(g)

4.15 × 10-3

Based on the reaction shown, which statement is true? N2 + O2 2 NO ̇H = 43.2 kcal A) 43.2 kcal are consumed when 1.00 g of NO is produced. B) 43.2 kcal are consumed when 1.00 g of N2 reacts. C) 43.2 kcal are consumed when 1.00 g of O2 reacts. D) 43.2 kcal are produced when 1.00 mole of NO is produced. E) 43.2 kcal are consumed when 1.00 mole of O2 reacts.

43.2 kcal are consumed when 1.00 mole of O2 reacts

Calculate the enthalpy for the following reaction: N2 + O2 2 NO given the following bond dissociation energies: N2 = 226 kcal/mol O2 = 119 kcal/mol NO = 145 kcal/mol.

55 kcal/mol

Based on the reaction shown, which statement is true? S + O2 SO2 + 70.8 kcal A) 70.8 kcal are consumed when 32.1 g of sulfur reacts. B) 70.8 kcal are consumed when 1 g of sulfur reacts. C) 70.8 kcal are produced when 1 g of sulfur dioxide is produced. D) 70.8 kcal are produced when 1 g of sulfur reacts. E) 70.8 kcal are produced when 32.1 g of sulfur reacts

70.8 kcal are produced when 32.1 g of sulfur reacts

Consider the reaction shown: N2 + O2 2 NO ̇H = 43.2 kcal When 50.0 g of N2 react, ________ kcal will be ________.

77.1; consumed

For the reaction given below, what quantity of heat will be produced if 90.0 g of C3H8 are consumed in the reaction? C3H8 + 5 O2 3 CO2 + 4 H2O + 488 kcal

996 kcal

Which of the following contains potential energy? A) person riding a bicycle B) a kid jumping rope C) a bouncing ball D) dancing E) a book on a table

A book on a table

Which of the following contains kinetic energy? A) bicylce at the top of a hill B) a moving car C) a piece of chocolate D) ball laying on the ground E) a battery

A moving car

Which of the following will affect all reaction rates? A) the temperature of the reactants B) the presence of a catalyst C) the concentrations of the reactants D) All are correct.

All are correct

A process or reaction which takes in heat from the surroundings is said to be

Endothermic

All of the statements concerning free energy and spontaneity are true except A) if the value of ̇G for a reaction is negative, the reaction is said to be spontaneous. B) enthalpy and entropy are of equal importance in determining the spontaneity of a reaction. C) a reaction which is nonspontaneous at low temperature cannot be spontaneous at higher temperatures. D) if the value of ̇G for a reaction is 55.2 kcal, the value of ̇G for the reverse reaction will be -55.2 kcal. E) the speed of a reaction is not influenced by its spontaneity

Enthalpy and entropy are of equal importance in determining the spontaneity of a reaction.

A solid sample at room temperature spontaneously sublimes forming a gas. This change in state is accompanied by which of the changes in the sample?

Entropy increases and energy decreases.

A process or reaction which releases heat to the surroundings is said to be

Exothermic

Which factors would decrease the rate of a reaction? I . Lowering the temperature II. Increasing the concentration of reactants III. Adding a catalyst

I only

Which factors would increase the rate of a chemical reaction? I . Increasing the temperature II. Removing products as they are formed III. Adding a catalyst

I, II, and III

Which of the following processes involve an increase in entropy of the system? I . Mothballs vaporize in a closet. II. Blocks are assembled into a house. III. Crystals grow from a sugar solution. IV. Recyclable plastics are sorted. V. Cake mix is manufactured from five basic ingredients.

I, V

All of the statements regarding the symbol ̇G are true except it A) allows us to identify an endergonic reaction. B) allows us to identify an exothermic reaction. C) describes the effect of both enthalpy and entropy on a reaction. D) allows us to predict the spontaneity of a reaction. E) refers to the free energy of the reaction.

It allows us to identify an exothermic reaction.

Which statement best describes the way a catalyst works? A) It increases the value of ̇H. B) It decreases the value of ̇H . C) It increases the value of ̇G. D) It decreases the value of Eact. E) It increases the value of Eact.

It decreases the value of Eact

Based on the bond energies given for each of the following which is the most stable? A) O=O 498 kJ/mol B) C=C 614 kJ/mol C) NXN 946 kJ/mol D) C=O 745 kJ/mol E) CXC 839 kJ/mol

NxN 946 kJ/mol

Which of the following statements can be assumed to be true about how reactions occur? A) Reactant particles must collide with each other. B) Catalysts must be present in the reaction. C) Energy must be absorbed as the reaction proceeds. D) More than one statement can be true.

Reactant particles must collide with each other.

Which of the following conditions characterizes a system in a state of chemical equilibrium? A) Concentrations of reactants and products are equal. B) Product concentrations are greater than reactant concentrations. C) Reactants are being consumed at the same rate they are being produced. D) Reactant molecules no longer react with each other. E) Rate of forward reaction has dropped to zero.

Reactants are being consumed at the same rate they are being produced

2 SO2(g) + O2(g) 2 SO3(g) + heat K = 4.8 × 1027 Which statement about this system is not true? A) Adding SO2 will cause an increase in the amount of SO3. B) The large value of K means that the reaction essentially goes to completion. C) Heating the system will cause breakdown of SO3. D) Removing O2 will cause an increase in the amount of SO3. E) At equilibrium SO3 is the predominant substance.

Removing O2 will cause an increase in the amount of SO3.

In order to determine if a reaction is at equilibrium which of the following must be true? A) The concentration of the products must be greater than the reactants. B) The forward and reverse reactions have stopped. C) The rate at which the forward and reverse reactions are proceeding are equal. D) The concentrations of the reactants and products must be equal. E) All of the above are true.

The rate at which the forward and reverse reactions are proceeding are equal.

Based on the reaction shown, which statement is true? 4 PCl3(l) P4(s) + 6 Cl2(g) ̇H = 304.0 kcal

When 1 mol P4 (s) is produced, 304.0 kcal are consumed

Based on the reaction shown, which statement is true? P4(s) + 10 Cl2(g) 4 PCl5(s) ̇H = -435.2 kcal A) When 30.97 g P4(s) react, 435.2 kcal are released. B) When 1 mol P4(s) reacts, 435.2 kcal are released. C) When 1 mol PCl5(s) is produced, 435.2 kcal are released. D) When 123.88 g P4(s) react, 435.2 kcal are consumed. E) When 208.22 g PCl5(s) are produced, 435.2 kcal are consumed

When 1 mol P4 (s) reacts, 435.2 kcal are released

Given the following reaction, the equilibrium expression will be: C(s) + 2 H2(g) CH4(g)

[CH4]/[H2]2

Consider the reaction: 2 CO(g) + O2(g) 2 CO2(g) The equilibrium expression for this reaction is: A) 2[CO2] 2[CO][O2] B) [CO2] [CO] + [O2] C) [CO][O2] [CO2] D) [CO2]2 [CO]2[ O2] E) [CO]2[ O2] [CO2]2

[CO2]2 [CO]2[O2]

Consider the reaction: A + 2 B 2 C + D The equilibrium expression for this reaction is: A) [A][B]2 [C]2[D] B) 2[C][D] [A]2[B] C) [C]2[D] [A][B]2 D) [A]2[B] 2[C][D] E) [A]2[B]2 2[C]2[D]

[C]^2[D] [A][B]^2

Write the equilibrium expression for the following reaction: 4 HNO3(l) 4 NO2(g) + 2 H2O(g) + O2(g)

[NO2]4 [H2O ]2 [O2]

Which of the following states of matter should have the lowest entropy value? A) a liquid B) a gas C) a crystalline solid D) Two of these have virtually the same entropy. E) all of the above

a crystalline solid

For a chemical reaction to occur, all of the following must happen except A) reactant particles must collide with the correct orientation. B) a large enough number of collisions must occur. C) chemical bonds in the products must form. D) reactant particles must collide with enough energy for change to occur. E) chemical bonds in the reactants must break.

a large enough number of collisions must occur.

All of the statements regarding the symbol "̇H" are correct except it A) can be called entropy change. B) can be called heat of reaction. C) has a negative value for an exothermic reaction. D) represents the difference between the energy used in breaking bonds and the energy released in forming bonds in a chemical reaction. E) can be called enthalpy change.

can be called entropy change.

A process which is unfavorable with respect to enthalpy, but favorable with respect to entropy could

could occur at high temperatures, but not at lower temperatures.

A reaction which is unfavorable with respect to entropy, but favorable with respect to enthalpy could

could occur at low temperatures but not at higher temperatures.

Which process is not likely to be considered reversible? A) melting wax to make candles B) a reaction using the symbol "" C) cutting down a tree D) dissolving salt in water E) a round trip to Las Vegas

cutting down a tree

In the reaction A + B AB, which of the following will not increase the rate? A) adding A B) adding a catalyst C) decreasing the temperature D) adding B E) increasing the temperature

decreasing the temperature

Activation energy can best be described as the

difference in energy between reactants and the maximum energy

In the reaction energy diagrams shown, reaction B is ________, and it occurs ________ reaction B.

endergonic; faster than

If heat is consumed during a reaction, the reaction is said to be

endothermic

Consider the reaction shown: 452 kcal + 4 PCl5(s) P4(s) + 10 Cl2(g) This reaction is ________ because the sign of ̇H is ________.

endothermic; positive

The concept of free energy allows prediction of spontaneity of a process by considering the changes in ________ and ________ during the process.

enthalpy; entropy

In the reaction energy diagrams shown, reaction A is ________, and it occurs ________ reaction B. 4

exergonic; slower than

A reaction is said to be ________ if the bonds formed during the reaction are stronger than the bonds broken.

exothermic

Consider the reaction shown: 2 CO(g) + O2(g) CO2(g) + 135.2 kcal This reaction is ________ because the sign of ̇H is ________.

exothermic; negative

Consider the reaction shown: C3H8 + 5 O2 3 CO2 + 4 H2O + 488 kcal We can say that this reaction is ________ and that the sign of ̇H is ________.

exothermic; negative

A rapid reaction is distinguished by

having a small value of activation energy.

The function of a catalyst in a reaction system is to

increase the rate of the reaction.

Entropy is used to

indicate the disorder of a system.

To simplify comparisons, the energy value of fuels is expressed in units of

kcal/g

Diatomic nitrogen is added to the equilibrium system: N2(g) + H2(g) 2 NH3(g) + heat When a new equilibrium is established the concentration of H2 will be ________ the amount at the original equilibrium, and the amount of NH3 will be ________ the amount at the original equilibrium.

less than; greater than

Which change to this reaction system would cause the equilibrium to shift to the right? N2(g) + 3 H2(g) 2 NH3(g) + heat

lowering the temperature

If we add a catalyst to the following equation, CO + H2O + heat CO2 + H2, which way will the equilibrium shift?

no effect

2 Al2O3(s) 4 Al(s) + 3 O2(g) ̇G = +138 kcal Consider the contribution of entropy to the spontaneity of this reaction. As written, the reaction is ________, and the entropy of the system ________.

non-spontaneous; increases

In the process of dissolving sugar in water, the entropy increases. This means that the sign of ̇S is ________, and that the randomness of the system ________.

positive; increases

A reaction that is spontaneous can be described as

proceeding without external influence once it has begun

For the following reaction, increasing the pressure will cause the equilibrium to 2 SO2(g) + O2(g) 2 SO3(g) + heat

shift to the right, towards products

The scientific principle which explains the observation that the amount of heat transfer accompanying a change in one direction is numerically equal but opposite in sign to the amount of heat transfer in the opposite direction is

the Law of Conservation of Energy.

Entropy can be defined as the

the amount of disorder in a system

The position of the equilibrium for a system where K = 4.6 × 10-15 can be described as being favored to ________; the concentration of products is relatively ________.

the left; small

When a reaction system is at equilibrium

the rates of the reaction in the forward and reverse directions are exactly equal

All of the statements are true for spontaneous reactions except A) the value of ̇G is less than zero. B) if the enthalpy change is unfavorable, they occur at a high temperature. C) the value of ̇G is unaffected by a catalyst. D) they are said to be exergonic. E) the reaction rate is determined by the value of ̇G .

the reaction rate is determined by the value of ̇G .

Reaction rates are determined by all of the following factors except the A) spontaneity of the reaction. B) number of collisions between molecules. C) orientation of collisions between molecules. D) activation energy of the reaction. E) force of collisions between molecules.

the spontaneity of the reaction.

Consider the endothermic reaction: N2(g) + 2 H2(g) N2H4(l) The entropy change of this reaction is ________ and the enthalpy change is ________, so at a very high temperature, this reaction is probably ________.

unfavorable; unfavorable; nonspontaneous

Which of the following can affect the activation energy of a reaction? A) use of a catalyst B) increase in concentration of reactants C) surface area of reactants D) increase in concentration of products E) temperature of the reaction

use of a catalyst