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)

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