Which of the following reactions is unfavorable at low temperatures but becomes

Question

Which of the following reactions is unfavorable at low temperatures but becomes favorable as the temperature increases? 2 CO(g) + O_2(g) rightarrow: delta H degree = -566 kJ; delta S degree = -173 J/K a. 2 H_2O(g) rightarrow 2 H_2(g) + O_2(g); delta H degree = 484 kJ; delta S degree = 90 J/K b. 2 N_2O(g) rightarrow 2 N_2(g) + O_2(g); delta H degree = -164 kJ; delta S degree = 149 J/K c. PbCL_2(s) rightarrow Pb^2+(aq); delta H degree = 23.4 kJ; delta S degree = -12.5 J/K The following reaction is spontaneous as written: Zn(s) + Cu^2+(aq) rightarrow Zn^2+(aq) + Cu(s) When a reaction is at equilibrium, which of the following statements is TRUE? Delta G = delta G^0 a. In K_eq = 0 b. delta G^0 = 0 c. Q = 0 d. delta G = 0

Explanation / Answer

Q17

In order for a reaction to be farourable:

G < 0

and

dG = dH - TdS

so

dH - T*dS < 0

negative dH, and positive dS, always spontaneous

a)

dG = dH - T*dS

dG = (-566) - (298)*(-173/1000) = -514

this favours products

b)

dG = dH - T*dS

dG = (484) - (298)*(90/1000) = 457

this favours reactants

c)

dG = dH - T*dS

dG = (-164) - (298)*(149/1000)

dG = --208.40, this favours

d)

dG = dH - T*dS

dG = (23.4) - (298)*(-12.5/1000)

dG = 27.125

this favorus reactants

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