Question

Which reaction is most likely to have a positive ΔSsys? Which reaction is most likely to have a positive ? 3NO2(g)+H2O(l)→2HNO3(l)+NO(g) CO(g)+Cl2(g)→COCl2(g) 6CO2(g)+6H2O(g)→C6H12O6(s)+6O2(g) 4NH3(g)+5O2(g)→4NO(g)+6H2O(g)

Answer 1

For ΔS to be positive the gas molecules of the products must be higher than reactants this lead to increase in disorder of the system:

3 NO₂(g) + H₂O(g) → 2 HNO₃(l) + NO(g) 
1 gas - 3 gas = - 2 gas mol

CO(g) + Cl₂(g) → COCl₂(g)
1 gas - 2 gas = -1 gas mol

6 CO₂(g) + 6 H₂O(g) → C₆H₁₂O₆(s) + 6 O₂(g)
6 gas - 12 gas = - 6 gas mol

4 NH₃(g) + 5 O₂(g) → 4 NO(g) + 6 H₂O(g)
10 gas - 9 gas = 1 gas mol
This one will have positive ΔS