a) H2(g) + 1/2O2(g) = H2O(l)
b) N2(g) + 3H2(g) = 2NH3(g)
c) HCl(g) = H^+(aq) + Cl^-(aq)
can anyone explain this to me ?
stilll not understanding how your suppose to get the answer?
1 Answer
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Entropy (ΔS) is a measure of molecular randomness or disorder of a system. If in a process disorder increases, the sign of ΔS is positive, if disorder decreases the sign is negative.
(a) two freely move gaseous reactants produce a liquid, a condensed form of matter. Disorder decreases. ΔS < 0.
(b) gaseous reactants form a gaseous product. But, 3 moles of reactant form 2 mole of product. Number of freely move particles decreases, dis order decreases, ΔS < 0.
(c) gaseous substance dissolves in water and produce 2 ions. Although it seems that disorder increases, it is not. Because you confine a freely move substance into a restricted volume. Its disorder decreases, ΔS < 0.
In order to calculate the ΔS values you will need a thermodynamic data.
ΔS = S final – S initial
(a) ΔS = S(H2O) – [S(H2) + 1/2S(O2)]
ΔS = 70 – [131 + 1/2(205)] = – 163.5 J/K.mol
(b) ΔS = 2S(NH3) – [S(N2) + 3S(H2)]
ΔS = 2×193 – [192 + 3(131)] = – 199 J/K.mol
(c) ΔS = [S(H+) + S(Cl-)] – S(HCl)
ΔS = [(0) + (57)] – (187) = – 130 J/K.mol
