[Parothwk20]

I am trying to find how many grams of CO2 are produced per 10,000 KJ of heat released by the combustion of butane, C4H10.

I am given

 2 C4H10 + 13 O2 => 8CO2 + 10H2O
 ΔHrxn = -5314KJ

I found ΔHf C4H10 = 346 KJ/mol

and now I am stuck

I have tried

 2 C4H10 => 10 H2 + 8 C
13 02 => 13 O2

And if I reverse the reaction and product i still find ΔHf C4H10 to equal 346 KJ/mol just opposite signs
 (exotherm vs endotherm)

[Borek]

I found ΔHf C4H10 = 346 KJ/mol

So how many moles of butane you have to burn to get 10 MJ?

[Parothwk20]

This might be an error in the book,

It says the ΔHrxn = -5314 kJ   (Should this be KJ/mol)

from there I said

-5314 = [8ΔHf(CO2) + 10ΔHf(H2O)] - [2ΔHf(C4H10) + 13ΔHf(02)]

I pulled these values from a table
ΔHf(O2) = 0
ΔHf(CO2) = -393.5 KJ
ΔHf(H20) = -285.5 KJ

Solved for ΔHf(C4H10) = 346 KJ


-5314 KJ/mol = [10molH2O (346KJ)/(180g H2O)] + [8mol CO2 (xKJ)/(352g CO2)]

Solved for x and I got 23.4g of CO2

[Padfoot]

You don't need any heats of formation for this question.

All you have to do is Borek's step then use balanced rxn eqn

[Borek]

I was slightly wrong again, you are a master of easy to overlook mistakes. 346 seems to be number of angels on the pinhead, not delta H for butane burning

2 C4H10 + 13 O2 => 8CO2 + 10H2O
 ΔHrxn = -5314KJ

In this reaction 2 moles of butane are burnt and there is 5314 kJ of energy produced.

How much energy is produced when 1 mole of butane is burnt?

How many moles of butane needs to be burnt to get 10 MJ of energy?

Now it is simple stoichiometry... Just answer these questions.