Question

Must Show all work

3. A key step in the production of sulfuric acid is the oxidation of SO2(g) to SO3(g):

2SO2(g) + O2(g) ----------> 2SO3(g)

At 298K, G= -141.6kJ; H=-198.4kJ; and S=-187.9J/K

a) Us the date to decide if this reaction is spontaneous at 25deg Cand predict how G will change with increasing T.

b) Assuming DH and DS are constant with increasing T, is the reaction spontaneous at 900deg C?

c) If the reaction reaches the equilibrium , calculate the temp.

Answer 1

a.)At, 25 deg C, the G for the reaction is negative, hence the reaction will be spontaneous

Also DG= DH-T(DS) , since S is negative, any temp increase would increase the value of G (make it less negative)

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b.)DG = DG= DH-T(DS) implies,DG @ 900deg C i.e 1173 K, DG= -198.4 -(1173*-187.9)/1000 (KJ)=-198.4+220.4067 =22KJ

NOT feasible @ 900 deg C as the DG is negative||(Note the division by 1000 for converting DS from J/K to kilo Joule per Kelvin and 900 deg C = 900 +273 = 1173 K)

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c)At Equilibrium, DG = 0 , i.e, DH-T*DS= 0 implies, DH = T*DS implies, T=DH/DS = -198.4 KJ/(-187.9/1000) KJ/K

= 1055.88K = 782.88 deg C