[lilns8252]

I dont understand how to solve these problems.. i got the two before these which are

--balanced equation of combustion reaction of methanol.
    CH₃OH(l)+ 3/2 O₂ ---> CO₂(g) + 2H₂O(g)

--Calculate the standard enthalpy change for the reaction, assuming H₂0 (g)  as a product.
             ANSWER : -638.5kJ

The two i don't understand :

1. Calculate the heat produced by combustion per liter of methanol. Methanol has a density of 0.791 g/mL.

 
2. Calculate the mass of  CO2 produced per  kJ of heat emitted.

[Arkcon]

Well, you have the enthalpy, in kJ for the reaction.  And the balanced chemical reaction.  What are the units, for the reaction, and the enthalpy?  What units are asked for in the question?  Can you convert?

[lilns8252]

Well i figure out the second qustion i needed it's just the first one left.. and the units they want the answer in is kJ/L... and yes i can convert..

[Arkcon]

Nope, that's not the direction I was trying to lead you.  You need the heat, in kJ.  You know how many kJ/mole.  You're given liters, and as a hint, they've given you methanol's density.  Do you see that you have to convert units, repeatedly, to get the answer?  How did you solve the second part?  You've already converted kJ, to moles, to grams, am I correct?