chemistry help me please???

Question

What is the minium kelvin temperature the system must be heated to to make the below reaction product favored ?



C (graphite) + CO2 (g) → CO (g)


What is the change in entropy (J/K-mol) for the universe of the above reaction at 25 oC ?

For the same reaction, what is the maximum useful work (kJ) that can be performed on the surroundings from the production of 4.3 moles of CO (g) ?

Answer 1

You need to figure out delta H and delta S, but balance the reaction first.

C + CO2 ---> 2 CO

delta H = 2 * Hf (CO) - Hf (CO2) = 2 * -110.5 + 393.5 = 172.5 kJ
delta S = 2 * So (CO) - So (C) - So * (CO2) = 2 * 197.6 - 5.74 - 213.6 = 175.9 J/K

For the reaction to be favored, delta G must be less than zero, therefore T * delta S must be greater than delta H. If delta G = 0, then:

delta H = T * delta S
T = delta H/delta S = 172.5/0.1759 = 980.7 K

Change in entropy is above; not sure about the useful work part.