Question

For a given reaction ΔH = 35.5kj mol-1 and Δs = 83.6jk-1 mol-1. The reaction is spontaneous at (assume as ΔH and Δs do not vary with temperature)

Answer 1

A reaction is said to be spontaneous if Gibb's free energy change is negative.

∆G < 0 => reaction is spontaneous.

∆G = ∆H - T∆S.

At ∆G = 0

∆H = T∆S

35.5 × 1000 = T × 83.6

( ∆H is. in KJ, so multiplied by 1000 to make it into J)

T = 424.64 K (nearly).

At 424.64 K, ∆G = 0

At a temperature higher than 424.64 K, ∆G becomes negative.

So, the reaction is spontaneous at a temperature higher than 424.64 K.

Hope, this helps you.