Question

Given the information Sº = 341.0 J/K AS = -120.0 J/K A+B - 2D AH = -757.9 kJ CD AH = 384.0 kJ calculate AGⓇ at 298 K for the reaction A+B +20 AG = TOOLS x10

Answer 1

Step 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) -2 * (reaction 2)

So, ΔHo rxn for required reaction will be:

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

= +1 * (-757.9) -2 * (384.0)

= -1525.9 KJ

Step 2:

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) -2 * (reaction 2)

So, ΔSo rxn for required reaction will be:

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

= +1 * (341.0) -2 * (-120.0)

= 581 J/K

Step 3:

ΔHo = -1525.9 KJ

ΔSo = 581 J/K

= 0.581 KJ/K

T = 298 K

use:

ΔGo = ΔHo - T*ΔSo

ΔGo = -1525.9 - 298.0 * 0.581

ΔGo = -1699 KJ

Answer: -1699 KJ