Chem: CHAP 7

look in practice

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A process or reaction which consumes heat

endothermic

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

N2 + O2 → 2 NO ΔH = 43.2 kcal Based on the reaction shown, which statement is true?

43.2 kcal are consumed when 1.00 mole of O2 reacts.

S + O2 → SO2 + 70.8 kcal Based on the reaction shown, which statement is true?

70.8 kcal are produced when 32.1 g of sulfur reacts

S + O2 → SO2 ΔH = -70.8 kcal Based on the reaction shown, which statement is true?

70.8 kcal are produced when 32.1 g of sulfur reacts.

Consider the reaction shown: N2 + O2 → 2 NO ΔH = 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 g of C3H8 are consumed in the reaction? C3H8 + 5 O2 → 3 CO2 + 4 H2O + 488 kcal

996 kcal

look in practice

A

look in practice

D

All of the statements concerning free energy and spontaneity are true except

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

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? 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 ΔG are true except

It allows us to identify an exothermic reaction.

All of the statements regarding the symbol ʺΔHʺ are correct except

It can be called entropy change.

Which statement best describes the way a catalyst works?

It decreases the value of Eact

2 SO2 (g) + O2 (g) ⇌2 SO3(g) + heat K = 4.8 × 1027 Which statement about this system is not true?

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

Sketch a diagram to illustrate the role of orientation in determining whether a collision between molecules of two different diatomic elements will lead to formation of a compound. How could you illustrate the influence of energy considerations on this reaction?

The diagram should show the two diatomic molecules touching each other so that the two pairs of different atoms are in contact. The drawing may also include lines showing that the bonds in the molecules of the elements are broken and new bonds form between the two different elements: X---X XX → | | O---O OO To illustrate the importance of energy, a heavy line could be used to indicate how hard the impact between X 2 and O2 is, using a darker or wider line for a stronger impact. Part of activation energy involves an impact with sufficient energy.

The label on a package of cookies states that there are 100 calories per serving. Explain the different meanings of this statement to a chemist and to a nutritionist. Be sure your answer explains the difference between kilocalories and Calories.

This statement means that the food energy contained in one serving of cookies is 100 kilocalories. A nutritionist calls one kilocalorie a Calorie; that is, a food Calories is really 1000 of the chemistsʹ calories.

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

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

P4 (s) + 10 Cl2 (g) → 4 PCl5 (s) ΔH = -435.2 kcal Based on the reaction shown, which statement is true?

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

Consider the reaction: 2 CO (g) + O2 (g) ⇌ 2 CO2 (g) The equilibrium expression for this reaction is

[CO2]2 [CO]2[O2]

Consider the reaction: A + 2 B ⇌ 2 C + D The equilibrium expression for this reaction is

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

For a chemical reaction to occur, all of the following must happen except

a large enough number of collisions must occur.

The amount of energy which must be invested in a reaction to get it started

activation energy

A state in which the rate of the forward reaction is exactly equal to the rate of the reverse reaction

chemical equilibrium

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

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 occur at low temperatures but not at higher temperatures.

Which process is not likely to be considered reversible?

cutting down a tree

In the reaction A + B → AB, which of the following will not increase the rate?

decreasing the temperature

A process or reaction that has a positive value of ΔG

endergonic

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

endothermic

A process or reaction which takes in heat from the surroundings 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 ΔH 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

A process or reaction that has a negative value of ΔG

exergonic

A process or reaction which releases heat

exothermic

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

exothermic

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

exothermic.

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

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

2 Al2O3 (s) → 4 Al (s) + 3 O2 (g) ΔG = +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 ΔS 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 ________ 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 amount of disorder in a system

Activation energy can best be described as

the difference in energy between reactants and the maximum energy.

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

the reaction rate is determined by the value of ΔG.

Reaction rates are determined by all of the following factors except

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