# how to calculate enthalpy of combustions using values of ΔHf

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#1
Hi guys,
So basically, I need to calculate enthalpy of combustion but I saw my values are in ΔHf/kjmol. SO now im confused as to how to do the enthalpy cycle, should I do it as just enthalpy of formation ? or are there further steps.

Basically would it look like this? or how would the arrows be and how would I deduce the enthalpy of combustion
Last edited by Fa123123; 1 month ago
0
1 month ago
#2
(Original post by Fa123123)
Hi guys,
So basically, I need to calculate enthalpy of combustion but I saw my values are in ΔHf/kjmol. SO now im confused as to how to do the enthalpy cycle, should I do it as just enthalpy of formation ? or are there further steps.

Basically would it look like this? or how would the arrows be and how would I deduce the enthalpy of combustion
You've kind of got confused with bond enthalpy, which shows the bottom line as gaseous atoms, and formation enthalpy.

Check out this video:

Last edited by charco; 1 month ago
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#3
(Original post by charco)
You've kind of got confused with bond enthalpy, which shows the bottom line as gaseous atoms, and formation enthalpy.

Check out this video:

sorry but that kind of confused me, I still do not understand, can you maybe help me out with a pic or example of this pls
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1 month ago
#4
1 sec this is what i did
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1 month ago
#5
(Original post by Fa123123)
Hi guys,
So basically, I need to calculate enthalpy of combustion but I saw my values are in ΔHf/kjmol. SO now im confused as to how to do the enthalpy cycle, should I do it as just enthalpy of formation ? or are there further steps.

Basically would it look like this? or how would the arrows be and how would I deduce the enthalpy of combustion
Enthalpy of combustion = enthalpy of formation of products - enthalpy of formatiom of reactants
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1 month ago
#6
Tbh Idk if this is right or not 😂
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1 month ago
#7
@smart ppl i.e CoochieMan xsowmix Hellohsjakodsmka cactus11235813 hop in here

also some1 check what i did pls
Last edited by .Dezer.; 1 month ago
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1 month ago
#8
(Original post by Hellohsjakodsmka)
Why am I on there 😂😂😂😂😂😂😂😂😂😂😂😂😂😂😂😭😭😭😭
typo
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im messin lol cus your smart asf? 😂
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1 month ago
#9
(Original post by .Dezer.)
@smart ppl i.e CoochieMan xsowmix Hellohsjakodsmka cactus11235813 hop in here

also some1 check what i did pls
it looks right
they've given formation data so the arrows shld be pointing upwards which op made a lil mistake on
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1 month ago
#10
(Original post by xsowmix)
it looks right
they've given formation data so the arrows shld be pointing upwards which op made a lil mistake on
wait is what i did right??
0
1 month ago
#11
(Original post by .Dezer.)
wait is what i did right??
yh yh it's right

why u surprised lol
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1 month ago
#12
(Original post by xsowmix)
yh yh it's right

why u surprised lol
idk cus i have always hated that topic my teacher actually sucks for inorganic so i have to teach myself it and this part of enthalpy changes always confused me but i finally get it now i think
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1 month ago
#13
(Original post by Hellohsjakodsmka)
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I'm really not.. i need to pm you ab chem actually
Spoiler:
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sure... go on im gonna go sleep soon so quick! if your free rn that is
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1 month ago
#14
(Original post by Hellohsjakodsmka)
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I'm in a "revision session" so I'll do it tmrw morning GO TO SLEEP dw about me x
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ok beautiful hehehe gn x
1
1 month ago
#15
(Original post by .Dezer.)
@smart ppl i.e CoochieMan xsowmix Hellohsjakodsmka cactus11235813 hop in here

also some1 check what i did pls
It looks correct to me chem is my worst subject tho soooo take what I just said lightly
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#16
(Original post by .Dezer.)
Tbh Idk if this is right or not 😂
thank you so much man!!! so i just needa keep my arrows up thats all. Was your answer 3117.8 kjmol-1
Last edited by Fa123123; 1 month ago
0
1 month ago
#17
(Original post by Fa123123)
thank you so much man!!! so i just needa keep my arrows up thats all. Was your answer 3117.8 kjmol-1
np man! I didnt get an answer as i didnt have the full question but if you follow the method i showed you, you defo got the answer right my guy

Peace
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