# Enthalpy Change helpWatch

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Thread starter 1 year ago
#1
Hey how would you calculate enthalpy change of formation from combustion data? Please could somebody explain this.
0
1 year ago
#2
(Original post by Orangee)
Hey how would you calculate enthalpy change of formation from combustion data? Please could somebody explain this.
by drawing a hess's law cycle
0
Thread starter 1 year ago
#3
(Original post by dip0)
by drawing a hess's law cycle
and then? I don’t understand this topic at all sorry
0
1 year ago
#4
(Original post by Orangee)
Hey how would you calculate enthalpy change of formation from combustion data? Please could somebody explain this.
You would use Hess' law. Here is an interactive on Hess' law. Work your way through it and if you still don't understand get back to us ...
1
1 year ago
#5
(Original post by Orangee)
and then? I don’t understand this topic at all sorry
so write down the combustion products of the reactants that are in their standard states.

Then go from reactants to the combustion products, then from there to products (but use - the enthalpy change here as we are going from combusted products to the final products rather than the other way around)
1
1 year ago
#6
The "elements" box is just the reactants in their standard states. Th enthalpy change from this would just be (483.6)+(-393.5)=90.1kj

the -483.6 has to change sign since the arrow is facing up to reactants instead of down

0
1 year ago
#7
(Original post by bluepound)
The "elements" box is just the reactants in their standard states. Th enthalpy change from this would just be (483.6)+(-393.5)=90.1kj

the -483.6 has to change sign since the arrow is facing up to reactants instead of down

This does not actually show combustion enthalpy at all!
0
Thread starter 1 year ago
#8
Thankyou
0
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