Predict the sign of the entropy change for the following processes. Give a reason for your prediction. (a) Pb2+(aq)+S2−(aq)⟶PbS(s) (b) 2Fe(s)+32O2(g)⟶Fe2O2(s) (c) 2C6H14(l)+19O2(g)⟶14 H2O(g)+12 CO2(g)

Question

Predict the sign of the entropy change for the following processes. Give a reason for your prediction.

(a) Pb2+(aq)+S2−(aq)⟶PbS(s)

(b) 2Fe(s)+32O2(g)⟶Fe2O2(s)

(c) 2C6H14(l)+19O2(g)⟶14 H2O(g)+12 CO2(g)

Answer 1

(a) Pb2+(aq)+S2−(aq)⟶PbS(s) Entropy will decrease going from aqueous to solid.

(b) 2Fe(s)+32O2(g)⟶Fe2O2(s) Entropy will decrease going from gas to solid

(c) 2C6H14(l)+19O2(g)⟶14 H2O(g)+12 CO2(g) Entropy will increase going from liquid to gas and from 19 moles of gas to 26 moles of gas.