Question

Given the information A+B C 2D D - AH = 627.2 kJ AH' = 535.0 kJ AS = 329,0J/K AS = -192.0 J/K calculate AG at 298 K for the reaction A+B — 20

Answer 1

Lets number the reaction as 1, 2, 3 from top to bottom

required reaction should be written in terms of other reaction

This is Hess Law

required reaction can be written as:

reaction 3 = +1 * (reaction 1) -1 * (reaction 2)

So, ΔHo rxn for required reaction will be:

ΔHo rxn = +1 * ΔHo rxn(reaction 1) -1 * ΔHo rxn(reaction 2)

= +1 * (627.2) -1 * (535.0)

= 92.2 KJ

So, ΔSo rxn for required reaction will be:

ΔSo rxn = +1 * ΔSo rxn(reaction 1) -1 * ΔSo rxn(reaction 2)

= +1 * (329.0) -1 * (-192.0)

= 521.0 J/K

We have:

ΔHo = 92.2 KJ

ΔSo = 521 J/K

= 0.521 KJ/K

T = 298 K

use:

ΔGo = ΔHo - T*ΔSo

ΔGo = 92.2 - 298.0 * 0.521

ΔGo = -63.058 KJ

Answer: -63.1 KJ