# What is the number you place to the left of the formula for a substance taking part in a reaction?

Jun 13, 2017

You may refer to the $\text{stoichiometric coefficient.........}$

#### Explanation:

We can examine coefficient with reference to a standard combustion reaction; say that of methane (i), or ethane (ii), as shown........

$C {H}_{4} \left(g\right) + {O}_{2} \left(g\right) \rightarrow C {O}_{2} \left(g\right) + 2 {H}_{2} O \left(g\right)$ $\left(i\right)$

${H}_{3} C - C {H}_{3} \left(g\right) + \frac{7}{2} {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right) + 3 {H}_{2} O \left(g\right)$ $\left(i i\right)$

For $\left(i\right)$ the stoichiometric coefficients are $\text{1, 1, 1, and 2}$.

And for $\left(i i\right)$ the stoichiometric coefficients are $\text{1, " 7/2, " 2, and 3}$.

And here these coefficients represent the stoichiometric proportions of reactants and products with reference to molar quantities.

All chemical reactions should be stoichiometrically balanced with respect to mass and charge............