Question

At what temperature will the following reaction happen spontaneously, given that ΔH = 8.91×103 J/mol and ΔS = –219.20 J/mol·K?

CaSO4(s) + 2HCl(g) → CaCl2(s) + H2SO4(l)

Answer 1

In order for a certain reaction to be spontaneous, the change in Gibb's free energy must be negative, that is:
dG < 0

We can calculate dG using:
dG = dH - dS

When we plug in the given values, we see that the sign of dG will never be negative; therefore, the reaction will not be spontaneous under any conditions.