Question

Which relationship or statement best describes ΔS° for the following reaction?

2NH3(g) + 2ClF3(g)  6HF(g) + N2(g) + Cl2(g)

A) S°  0

B) S° < 0

C) S° > 0

D) S° = H°/T

E) More information is needed to make a reasonable prediction

the boxes are deltas

Answer 1

If a reaction involves only gases, the entropy is related to the total no. of moles in either side of the reaction. If there is a decrease in no. of moles on the product side, that means change in entropy will be negative, if there is an increase that would mean positive entropy.

The reaction is,

2NH3(g)+2ClF3(g)----> 6HF(g)+N2(g)+Cl2(g)

So, moles on the reactant side = 2+2 = 4

Moles on the product side = 6+1+1 = 8

Since, the number of moles on product side is greater, that would mean positive deltaS

So, deltaS>0 option C