Question

What needs to happen for the equation CH4 + O2 → CO2 + H2O to be balanced?

A. A coefficient of 2 must be added before both products.

B. A coefficient of 2 must be added before the second reactant and the second product.

C. Nothing, the equation is already balanced.

D. A coefficient of 2 must be added before both products and reactants.

Answer 1

The answer is B.
in the original equation, CH4 + O2 → CO2 + H2O, there are:

REACTANTS: 2 carbon, 4 hydrogen, 2 oxygen
PRODUCTS: 2 carbon, 2 hydrogen and 1 oxygen.

If we change the equation to this,
CH4 + 2O2 → CO2 + 2H2O, then there are now:

REACTANTS: 2 carbon, 4 hydrogen, 4 oxygen
PRODUCTS: 2 carbon, 4 hydrogen, 4 oxygen
and thus the equation is balanced