I am to use this formula to find ΔH°f,methane:
ΔH°comb=2ΔH°f,water+ΔH°f, carbon dioxide-ΔH°f,methane-2ΔH°f,oxygen
For ΔH°comb, the value is 884 KJ/mol
For ΔH°f,water, the value is -285.8
For ΔH°f,carbon dioxide, the value is -393.5
I was not given ΔH°f,oxygen, what value would it be?
The pure element is zero. All elements in their standard state are zero.
To find the value of ΔH°f,oxygen, we can rearrange the equation you provided:
ΔH°comb = 2ΔH°f,water + ΔH°f,carbon dioxide - ΔH°f,methane - 2ΔH°f,oxygen
Let's substitute the values we already know:
884 KJ/mol = 2(-285.8) + (-393.5) - ΔH°f,methane - 2ΔH°f,oxygen
Now, let's solve for ΔH°f,oxygen:
- ΔH°f,methane - 2ΔH°f,oxygen = 884 KJ/mol - 2(-285.8) - 393.5
Simplifying further:
- ΔH°f,methane - 2ΔH°f,oxygen = 884 + 571.6 - 393.5
- ΔH°f,methane - 2ΔH°f,oxygen = 1062.1 KJ/mol
Now, since we were not given the value of ΔH°f,methane, we cannot calculate the exact value of ΔH°f,oxygen. However, we can rearrange the equation once again to find the general relationship:
ΔH°f,oxygen = (ΔH°comb - 2ΔH°f,water - ΔH°f,carbon dioxide + ΔH°f,methane) / -2
If you are given the value of ΔH°f,methane, you can substitute it into this equation to find the value of ΔH°f,oxygen.