Determine the free energy change for each of the following reactions, which are run under standard state conditions and 25 °C. Identify each as either spontaneous or nonspontaneous at these conditions.

a. MnO2(s)→ Mn(s) + O2(g)
b. H2(g) + Br2(l) → 2HBr(g)
c. Cu(s) + S(g)→ CuS(s)
d. 2LiOH(s) + CO2(g) → Li2CO3(s) + H2O(g)
e. CH4 + O2(g)→ C(s, graphite) + 2H2O(g)
f. CS2(g) + 3Cl2(g) → CC14(g) + S2C12(g)