Question

For which reaction is delta Ssys > 0?

A) CH4(g) + 2 O2(g) ¨ CO2(g) + 2 H2O(l)

B) NH3(g) + HCl(g) ¨ NH4Cl(s)

C) 2 NH4NO3(s) ¨ 2 N2(g) + O2(g) + 4 H2O(g)

D) HCl(aq) + NaOH(aq) ¨ NaCl(aq) + H2O(l)

Answer 1

dS is + (i.e., >0) when S products is greater than S for reactants.
A has 3 mols gas on the left and 1 on the right; therefore, dS decreases.
Remember S increases from solids to liquids to gases. Therefore, A and B can't be right.