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Calculating the amount of released energy.
moreche28:
There's a chemistry problem I'm trying to solve. Burning 1 kg of syntin or 1 kg of hydrogen will release more E? We predict that syntin decomposes into H2O and CO2. Their standard ΔH of formation: ΔH (CO2, g) =-393,5kJ/mol; ΔH(H2O) =-241,8 kJ/mol. Many thanks! :)
Borek:
You have to show your attempts at solving the problem to receive help, this is a forum policy.
moreche28:
Oh, thank you. :) I will do so.
Enthalpy:
The usual combustion of Syntin is with pure oxygen, and despite high pressure, the high temperature makes about as much CO as CO2.
Anyway, you can compute a heat of combustion, or you can answer qualitatively that the same mass of hydrogen releases more combustion heat than a hydrocarbon, because it contains many more moles. I know no exception. The margin is big.
"Energy" isn't accurate enough, and "E" seems to designate the internal energy in some countries. You're probably talking about the enthalpy H.
moreche28:
Thank you, sir. :) So, I thought about a possible way how to calculate it... Here it is.
a) Burning 1 kg of H2.
2 H2 (g) + O2 (g) => 2 H2O (g)
Mr = 2
Q1 = 2 . - 241,8 = - 483,6 kJ.mol-1
n = m/M = 1000 g / 2 g.mol-1 = 500 mol
E = 500 . - 483,6 = - 241 800 kJ = - 241,8 MJ
b) Burning 1 kg of syntin.
C10H16 + 14 O2 => 10 CO2 + 8 H2O
Mr = 136,238
Q2 = (10 . – 393,5) + (8 . - 241,8) = - 5889,4 kJ.mol-1
n = m/M = 1000/136,238 = 7,34 mol
E = 7,34 . - 5889,4 = - 43228,196 kJ = - 43,228196 MJ.
Is that right? :D I presume not, but otherwise I cannot come to any other solution. Thanks.
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