SmartBook Ch. 17

A(n) _____ process is one that will occur without a continuous input of energy under a given set of conditions.

spontaneous

If a given reversible reaction has positive values for both ΔH and ΔS, the value of ΔG will become _____ negative as temperature increases, and the formation of the _____ will be increasingly favored.

more; products

In order for the products to be favored in a reaction, the value of the standard free-energy change (ΔGo) must be _____.

negative

As the reaction quotient Q increases, what is the effect on the spontaneity of the reaction?

The reaction becomes less spontaneous.

A reaction is found to be spontaneous only above a particular temperature. Which of the following must be true? Select all that apply.

ΔHorxn > 0 ΔSorxn > 0

A reaction taking place at 100oC has an entropy change of 200 J/K and an enthalpy change of -20 kJ. Which of the following expressions would be used to calculate ΔG under these conditions?

-20,000 - (373)(200)

Calculate the value of ΔG for a reaction at 75oC whose enthalpy change is 50 kJ and whose entropy change is 100 J/K.

15.2 kJ

What is a spontaneous process?

A process that occurs under specified conditions without a continuous input of energy

Which statements about the relationship between Q, K, and ΔG are correct? Select all that apply.

If Q is greater than K, then the value of ΔG will decrease as the reaction proceeds. If Q is less than K, then the value of ΔG is less than zero.

Match the relative values of Q and K with the associated value of ΔG.

Q < K --> ΔG < 0 Q > K --> ΔG > 0 Q = K --> ΔG = 0

Given the balanced chemical equation CH4(g) + 2O2(g) → CO2(g) + 2H2O(g), which of the following equations should be used to calculate the total entropy change for this reaction? (States of matter have been omitted for simplification.)

S[CO2] + 2(S[H2O]) - S[CH4] - 2(S[O2])

Which of the following is a correct description of the third law of thermodynamics?

The entropy of a perfect crystalline substance is 0 at 0 K.

Which of the following options correctly describe the behavior of a reversible reaction for which both ΔH and ΔS < 0? Select all that apply.

The formation of the reactants will become increasingly favored as the temperature rises. At low temperatures, ΔGrxn < 0. The reaction will become less spontaneous as the temperature increases.

If the reaction shown below is to be coupled to a second reaction in order to generate an overall spontaneous process, what must be true regarding this second reaction? Fe2O3(s) → 2 Fe(s) + 3/2 O2(g); ΔG = 740.98 kJ

The free-energy change must be more negative than -740.98 kJ.

Which of the following statements correctly explain the increase in entropy that occurs when a substance changes from a solid to liquid, or liquid to gas? Select all that apply.

The freedom of movement of the particles increases in the change solid → liquid → gas. The energy of the particles increases during these phase changes.

Which of the following options correctly explain the impact of ΔHsys on the entropy change of the surroundings? Select all that apply.

The lower the temperature, the greater the effect of ΔHsys on the entropy of the surroundings. At high temperature, the enthalpy change of the system will have a relatively small effect on the entropy of the surroundings.

Which of the following options correctly describe standard entropy? Select all that apply.

The units of standard entropy are J/(mol*K) The standard entropy of a substance is its absolute entropy at 1 atm.

Which of the following must be known in order to assess the spontaneity of a chemical reaction or physical process at a particular set of conditions?

change in entropy change in enthalpy reaction temperature

The third law of thermodynamics states that a perfect _____ of a pure solid substance has _____ entropy at a temperature of 0 K.

crystal zero

Consider the equation ΔG = ΔGo + RTlnQ. If a given process is proceeding such that the value of the reaction quotient Q is decreasing, then the value of ΔG is _____, and the process is becoming _____ spontaneous as it proceeds.

decreasing more

The first law of thermodynamics states that _____ is always conserved.

energy

In order to predict whether the reaction below will be spontaneous under a given set of conditions, the change in both ______ and ______ for the process under those conditions must be known. N2(g) + 3H2(g) → 2NH3(g)

enthalpy; entropy

The second law of thermodynamics states that the total _____ of the universe will _____ for any spontaneous process.

entropy; increase

True or false: For an element in its standard state, the standard entropy So is equal to 0 J/mol⋅K.

false

The _____ law of thermodynamics states that _____ can neither be created nor destroyed.

first energy

The Gibbs _____ energy change (symbolized by Δ_____) is a measure of the spontaneity of a process, and of the useful energy available from it.

free G

An exothermic reaction releases heat to the surroundings, causing a(n) _____ in the movement of the particles in the surroundings. The entropy of the surroundings will therefore _____.

increase; increase

The change in entropy for a given process can be calculated by subtracting the _____ entropy of the system from the _____ entropy of the system.

initial final

If a given process proceeds spontaneously toward the products, the value of the reaction quotient Q is _____ the equilibrium constant K, and ΔG for the reaction will be _____.

less than; negative

For a chemical reaction, ΔSorxn = ΣnSo(_____) - ΣnSo(_____).

products reactants

A reaction with a positive value of ΔGo will favor _____ at equilibrium, while a reaction with a negative value of ΔGo will favor _____ at equilibrium.

reactants products

The _____ law of thermodynamics states that a spontaneous process will result in an increase in the entropy of the universe.

second

Which changes in state will result in an increase in the entropy of a substance? Select all that apply.

solid to vapor solid to liquid liquid to vapor

The _____ entropy of a substance is its absolute entropy at 1 atm.

standard

The Gibbs free energy change ΔG allows us to determine the spontaneity of a process based on thermodynamic changes to the ______.

system only

The ______ law of thermodynamics states that the entropy of a perfect crystal at a temperature of 0 K is equal to zero.

third

The sign of which quantity indicates whether or not a particular reaction or process will occur spontaneously?

ΔG

Match each thermodynamic quantity with the information it provides about a given reaction.

ΔGo > 0 --> reactants favored ΔG < 0 --> spontaneous ΔG > 0 --> nonspontaneous ΔGo < 0 --> products favored

Match each free-energy term with its correct definition.

ΔGrxn --> any conditions ΔGorxn --> standard conditions

Which of the following symbols denotes a standard free-energy change of reaction?

ΔG°rxn

A reaction is found to be spontaneous only below a particular temperature. Which of the following must be true? Select all that apply.

ΔHorxn < 0 ΔSorxn < 0

Which of the following options correctly show how to calculate the entropy change of a system?

ΔS = Sf - Si ΔS = k ln(Wf/Wi)