combustion rxn

[Jesse H 2L]

What was the equation that Lavelle shared for calculating the change in mols for a combustion rxn?

[lilymayek_1E]

I don't remember having written down a specific equation, but combustion problems should probably ask for expansion/work of the gaseous products, and if you know the chemical equation as well as the starting number of moles for one of the reactants, you can. An example of this is the reaction C6H6(s) + 15/2O2(g) = 6CO2(g) + 3H2O(l). the question asks for the gaseous products and also gives us that there is 1.00 mol of C6H6 present. From this, since we're focusing on the gaseous products, you can determine that for 1 mol of C6H6, 7.5. mols of O2 are used and 6 mols of CO2 are produced. In gaseous products, you can find that the change of mols is -1.5 mols.

[Nick Lewis 4F]

What was the equation that Lavelle shared for calculating the change in mols for a combustion rxn?

I dont remember exactly what you're referencing, but it is relatively straight forward to calculate the change in moles in a combustion reaction, just make sure you identify the right stoichiometric coefficients to support your equation because that's the trickiest part.