# Heat generated

#### Hamal_Arietis

1. Homework Statement
The heat of combustion of graphite and that of CO is 394kJ/mol and 283 kJ/mol, respectively. When 12g of graphite is combusted incompletely, the same volume of CO and CO2 are generated. Calculate the heat of generated by this combustion. Choose the closet value.(kJ)
A.197 B.253 C.308 D.339 E.505 F.677

2. Homework Equations
The answer is B.253kJ
3. The Attempt at a Solution
My idea is:
$C+O2→CO\\ 1 \qquad \qquad 1$ and $ΔH_1=-394kJ/mol$
$CO+O2→CO2\\ 0,5 \qquad \qquad 0,5$ and $ΔH_2=-0,5.283 kJ/mol$
So $ΔH=ΔH_1+ΔH_2=-535,5kJ/mol$
Where is my wrong?
Thanks for helping

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#### Bystander

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Where are my wrong?
The answer is B.253kJ
Wrong.
Ask yourself, "How many moles of carbon have been burned? How many moles of gaseous products have been formed? What is the minimum heat?"

#### Hamal_Arietis

How many moles of gaseous products have been formed?
I think 0,5 mol CO and 0,5 mol CO2 are generated and 1 mol C is combusted

#### Bystander

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I think 0,5 mol CO and 0,5 mol CO2 are generated and 1 mol C is combusted
Correct. And the minimum heat released is what?

#### Hamal_Arietis

Correct. And the minimum heat released is what?
I don't know.
$C+O2→CO\\ 1 \qquad \qquad 1$ and $ΔH_1=-394kJ/mol$
$CO+O2→CO2\\ 0,5 \qquad \qquad 0,5$ and $ΔH_2=-0,5.283 kJ/mol$
So $ΔH=ΔH_1+ΔH_2=-535,5kJ/mol$
1 mol of C is combusted and 0,5 mol of CO and CO2 are generated . So the heat is -535,5kJ/mol?

#### Bystander

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What's half a mol x 394 kJ/mol?

#### Hamal_Arietis

What's half a mol x 394 kJ/mol?
197kJ/mol
but 1 mol C is burned, not 0,5 mol. And 1mol CO is generated but 0,5 mol CO is burned and 0,5 mol CO2 is generated.

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Yes, and ....

"Heat generated"

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