For which of the following reactions is S° > 0. Choose all that apply. NH4I(s) NH3(g) + HI(g) CH4(g) + H2O(g) CO(g) + 3H2(g) 2NH3(g) + 3N2O(g) 4N2(g) + 3H2O(g) 2NH3(g) + 2O2(g) N2O(g) + 3H2O(l) CO(g) + Cl2(g) COCl2(g)

Entropy is the measure of randomness or disorder of a system. If a system moves from an ordered arrangement to a disordered arrangement, the entropy is said to decrease and vice versa.

1. [tex]NH_4I(s)\rightarrow NH_3(g)+HI(g)[/tex] : As in this reaction 1 moles of solid reactants are converting to 2 moles of gaseous products. The randomness will increase and hence entropy will also increase. Thus [tex]\Delta S[/tex] > 0.

2. [tex]CH_4(g)+H_2O(g)\rightarrow CO(g)+3H_2(g)[/tex]: As in this reaction 2 moles of gaseous reactants are converting to 4 moles of gaseous products. The randomness will increase and hence entropy will also increase. Thus [tex]\Delta S[/tex] > 0.

3. [tex]2NH_3(g)+3N_2O(g)\rightarrow 4N_2(g)+3H_2O(g)[/tex]: As in this reaction 5 moles of gaseous reactants are converting to 7 moles of gaseous products. The randomness will increase and hence entropy will also increase. Thus [tex]\Delta S[/tex] > 0.

4. [tex]2NH_3(g)+2O_2(g)\rightarrow N_2O(g)+3H_2O(g)[/tex]: As in this reaction 4 moles of gaseous reactants are converting to 4 moles of gaseous products. The randomness will increase and hence entropy will also increase. Thus [tex]\Delta S[/tex] > 0.

5. [tex]CO(g)+Cl_2(g)\rightarrow COCl_2(g)[/tex]: As in this reaction 2 moles of gaseous reactants are converting to 1 mole of gaseous products. The randomness will decrease and hence entropy will also increase. Thus [tex]\Delta S[/tex] < 0.