[rosebudd88]

Water gas, a mixture of carbon monoxide and hydrogen, is produced by treating carbon (in the form of coke or coal) with steam at high temperatures.

C(s) + H2O(g)  CO(g) + H2(g)

Not all the carbon available is converted to water gas as some is burned to provide the heat for the endothermic reaction of carbon and water. What mass of carbon (give units) must be burned (to CO2 gas) to provide the heat to convert 1.00 kg of carbon to water gas?


Where should I start?

Should I be finding the ΔH° for the formation of CO2 and then
using the two equation with hess's law?

[curiouscat]

Find deltaH for both reactions. You need enough of the exothermic rxn to compensate for the endothermic rxn.

[rosebudd88]

Ok, I came up with something, And i Feel pretty good about it

Here it is

(1st)  C(s) + H2O(g) = CO(g) + H2(g)  ΔH°=131.3 kJ/mol

I found out the ΔH° from the Δ_fH° values in the book
-this reaction absorbs 131.3 kJ/mol (endothermic)

(2nd) C(s) + O2(g) = CO2(g)  ΔH°= -393.5 kJ/mol

I came up with this equation and just used the book value for CO2(g)

NOW

Since 1000g of carbon is really 83.257 mols of C

My reasoning:

The (1st equation) requires 131.3 Kj/ 1 mol of C(s)
to convert 1Kg of C to water gas we need 83.257 mols of C = 10931.644 Kj of energy to be absorbed

And for 1 mol of C to convert into 1 mol of CO2(g) -393.5 Kj are released for each mole of C(s) [according to the 2nd equation]

So if the reaction take 10931.644 kJ, then divide that by -393.5 kJ/mol
this will equal the number of mols of C(s) required to burn.
=27.7805 mols of C(s) required to convert 1 kg of c(s) to water gas.
so take those moles and convert them in to g
=2.31 g C

Is this right?

Ok I was just informed 2.31 g is not the right answer,
Any more suggestions, where did i go wrong?

[rosebudd88]

Do I have the second equation wrong?
Should i Really be using
2CO(g) + O2(g) = 2CO2(g) ΔH°=-566 kJ/2 mol CO2(g)

then the ΔH°= -283 kJ/ mol CO2(g)

Is this what i should be using?

I am I heading in any right direction?