[Fish200398]

24 g graphite burned incompletely, 14g CO dan 66 g CO2 are produced.
C + O2 = CO2 394kJ
CO + 1/2O2 = CO2 283 kJ
A. Calculate heat of formation of CO
B. How much heat energy is generated by this reaction?

I can answer for A, 111kJ the answer. But what about B? What does it mean?

[chenbeier]

B is the sum of both reactions.

[Fish200398]

Ok. The answers to choose is 505kJ, 646.5 kJ, 702kJ, 788kJ, 843.5kJ

[Fish200398]

What 'this reaction' refers to?

[mjc123]

24 g graphite burned incompletely, 14g CO dan 66 g CO2 are produced.

[Fish200398]

Sum of the 2 is 394+283 = 677kJ there is no exactly same in the answer?

[mjc123]

You don't just sum the two. What reactions are going on (where does the CO come from?), and how much of each?

[AWK]

You have the molar heat of combustion C to CO2 given. You calculated the molar heat of combustion C to CO.
In the combustion reaction, you received 0.5 mol CO and 1.5 mol CO₂ (the numbers can be calculated in memory without a calculator).
How much heat energy is generated by this reaction?

[Fish200398]

1.5 x 394 kJ? Because CO2 is 1.5 mol.
And 0.5 x 283kJ? Because CO is 0.5 mol thus CO2 is 0.5 mol?
But i get 732.5 kJ?

[AWK]

283kJ

[Fish200398]

1.5x394kJ and 0.5x111kJ and it is 646.5kJ. Is the heat of formation of CO2 the same as heat of combustion of CO2 ?

[AWK]

Just think
C + 1/2O₂

[Fish200398]

I dont get it. What do you mean? What i mean is, we use heat formation of CO that is 111kJ, then we sum it with heat formation of CO2 right? But known info is heat combustion of CO2. So is it the same thing heat combustion and heat of formation of CO2?

[mjc123]

CO₂ can't be combusted. The heat of formation of CO₂ is the same as the heat of (complete) combustion of C, i.e. the heat of the reaction
C + O₂  CO₂

[Fish200398]

Thanks mjc123