chapter 16

Calculate ΔSofor reaction below at 25oC, given that the standard entropies at 25oC for O2(g), CO(g), and diamond are 205.0 J/mol. k , 197.9 J/mol. K and 2.43 J/mol. K 2 C(diamond) + O2(g) → 2 CO(g)

+ 185.9

Use the standard free energies of formation to calculate ΔGrxno for the reaction below. Mg(s) + N2O(g) ⟶ MgO(s) + N2(g) Substance. ΔGfo(kJmol) N2O(g) 103.7 MgO(s). -569.3

- 673.0 kJ

A reaction has a ΔHrxn = 54.2 kJ. Calculate the change in entropy for the surroundings (ΔSsurr) for the reaction at 25.0oC. Assume constant pressure and temperature.

-182 J/K

Estimate the temperature above which the reaction below is spontaneous. The ΔSo for the reaction is 16.1 J/K. CH4(g) + N2(g) + 163.8 kJ → HCN(g) + NH3(g)

10.2 x 103 K

A reaction has an equilibrium constant of Kp = 0.018 at 25oC. Determine ΔGrxnofor the reaction at this temperature.

9.96 kJ

Arrange the gases the following gases in order of increasing standard entropy (So) at 298 K. F2, Ar, CH3F

Ar < F2 < CH3F

Which of the following substances has/have a standard free energy of formation equal to zero?

H2(g)

Under which set of conditions is ΔGrxn for the reaction A(g) ⟶ B(g) most likely to be negative?

PA = 5.00 atm; PB =0.050 atm

A certain process has a ΔSuniv>0 at 25oC. Which of the following is true about the process?

The process is spontaneous at 25oC.

Thermodynamics cannot provide information about which of the following?

The speed of a reaction.

The thermodynamic function that describes the degree of freedom of motion of particles in a system and the dispersal of their energy of motion is _______________

entropy

When a system is at equilibrium _____________________

neither the forward nor the reverse process is spontaneous

The enthalpy change and standard entropy change for the reaction below are ΔH= 137 kJ and ΔSo= 120 J/K. C2H6(g) → C2H4(g) + H2(g) This reaction will be _____________.

spontaneous only at high temperature

If ΔGo for a reaction is greater than zero, then ____________.

the equilibrium constant for the reaction is smaller than one

A reaction that is spontaneous ______________________

will proceed as written without outside intervention

A reaction that is spontaneous ________________________

will proceed as written without outside intervention

The sign of ΔHrxn and ΔSrxn for several different reactions are given below. In which case is the reaction spontaneous at all temperatures?

ΔHrxn < 0 and ΔSrxn> 0