Question

What is the whole number that appears before a formula in an equation?

Answer 1

Do you mean the `"stoichiometric coefficients"`?

Explanation:

Let's take hydrocarbon combustion, that of pentane, which we could represent as:

`C_5H_12(l) + 8O_2(g) rarr 5CO_2(g) + 6H_2O(l)`

The numbers: `1,8,5,` and `6` are the stoichiometric coefficients of `"pentane, dioxygen, carbon dioxide, and water"` in the stoichiometrically balanced equation.

For even numbered alkanes, we could use non-integral stoichiometric coefficients:

`C_6H_14(l) + 19/2O_2(g) rarr 6CO_2(g) + 7H_2O(l)`

Is this equation stoichiometrically balanced? Don't trust my arithmetic!