[John623]

Let's say I have the following equation:

CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l)

I know that if I want to turn it into a thermochemical equation I need to add ΔH but I'm not sure when you add all the other details such as if it's combustion and if it was done at standard conditions. For example.

I assume this is the thermochemical equation:
CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH = -890kJ/mol

Is this still a thermochemical equation now i've added some extra details?
CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH°_c = -890kJ/mol

What type of equation do I here when I put in the details of what I burned? I'm no sure if I should be doing this or not.
CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH°_c CH₄(g) = -890kJ/mol

Does this type of equation have a name?
 ΔH°_c CH₄(g) = -890kJ/mol

[Borek]

I feel like you are making similar mistake as it was with the cell notation - you assume there is a highly precise definition of how the "thermochemical equation" should be written. I am not aware of one.

Technically reaction of hydrocarbon with oxygen (one the goes to the end and produces H₂O and CO₂) is combustion, you don't have to name it as such. Zero in ΔH° means it is given for STP.

CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH = -890kJ/mol

Combustion, conditions not clear.

CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH°_c = -890kJ/mol

Assuming _c means combustion, this information is duplicated - it is obvious you are talking about combustion from the reaction equation.

CH₄(g) + 2O₂(g)  CO₂(g) +2H₂O(l) ΔH°_c CH₄(g) = -890kJ/mol

Again, plenty of information repeated.

ΔH°_c CH₄(g) = -890kJ/mol

This is quite sufficient - while it doesn't give an exact reaction, there is only one combustion reaction for CH₄, and every chemist knows what it is.

There is one problem left - sometimes when you balance combustion reaction, hydrocarbon will require a coeffcient of 2

2C₂H₂ + 5O₂ 4CO₂ + 2H₂O

Then, if the enthalpy is listed as ΔH°_c it can be slightly ambiguous - is it per mole of the hydrocarbon, or is it "per mole of reaction as written"? It is good to clarify the situation in such cases but explicitly explaining what you mean.