Homework Sourse3NO2 g H2Ol 2HNO3aq NO g Cr2O3 s 3CO g 2Cr s 3O2g SO2g 12
3NO2 (g)+ H2O(l) ----> 2HNO3(aq) + NO (g)
Cr2O3 (s) + 3CO (g)-> 2Cr (s) 3O2(g)
SO2(g) +1/2O2 (g) -----> SO3 (g)
N2O4(g) 4H2 (g) ----> N2 (g) 4H2O(g)
Solution
Recall that the change in entropy is given by
dS = Sproducts - Sreactants
3NO2 (g)+ H2O(l) ----> 2HNO3(aq) + NO (g)
SRxn = 2HNO3 + NO- (3NO2+ H2O)
SRxn = 2+(155.6) + 210.8 - (3*240.1 + 70)
Srxn = -268.3 J/K
b) Cr2O3 (s) + 3CO (g)-> 2Cr (s) 3O2(g)
SRxn = 2*Cr + 3*O2 - (Cr2O3 + 3CO)
SRxn = 2*23.8 + 3*205.5 - (81.2 + 3*197.7) = -10.2 J/K
c)
SO2(g) +1/2O2 (g) -----> SO3 (g)
SRxn = Sprod - Sreact
SRxn = SO3 - (SO2 + 1/2O2)
Srxn = 256.8 - (248.2 + 1/2*205.5) = -94.15 J/K
d)
N2O4(g) 4H2 (g) ----> N2 (g) 4H2O(g)
SRxn = N2 + 4H2O - (N2O4 + 4H2)
Srxn = 191.6 + 4*188.8 - (304.4 + 4*130.7)
Srxn = 119.6 J/K
