Help..... calculating kp value

Question

Is carbon dioxide a viable source of the fuel CO? Pure carbon dioxide (PCO2 = 1 atm) decomposes at high temperatures. For the system

2 CO2 (g) ⇔ 2 CO (g) + O2 (g)

the percentage of decomposition of the CO2 (g) changes with temperature as follows:

Temperature (K) Decomposition (%)
1500                      0.048
2500                       17.5
3000                      54.8

a. Is the reaction endothermic or exothermic?

b. Calculate Kp at each temperature and discuss the results?

c. Is the decomposition of CO2 an antidote for global warming?

Answer 1

Set up an ICE table:

......2 CO2 (g) ⇔ 2 CO (g) + O2 (g) 

I... 1 atm..........0.............0.........

C...0.00048....+0.00048....+0.00024.....

E..1-0.00048.....0.00048........0.00024...

K = (0.00048)^2(0.00024)/(0.99952)^2

K = 5.5x10^-11 at 1500ºK

 

Do the same at 2500º and at 3000º

K @ 2500 = 3.9x10^-3

K @ 3000 = 4x10^-1

 

The reaction would be endothermic.  Decomposition reactions are for the most part, endothermic.  Heat is added and as more heat is added (higher temperatures) the Kp becomes larger, meaning more products are formed.

 

It's unlikely that this decomposition reaction of CO2 would be useful in combating global warming, if, in fact, global warming is a result of CO2.  The extremely high temperatures (almost 5,000ºF) to get 55% decomposition is unreasonable.