? I JUST DONT UNDERSTAND

5SiO2 + 2CaC2 → 5Si + 2CaO + 4CO2

Explanation:

When you are balancing an equation, you use coefficients to change the number of atoms of each type that are on each side of the equation.

You cannot change subscripts, the small numbers to the right of the substances. You can only add coefficients, the large numbers to the left of substances.

A balanced equation has the same number and type of atoms on both sides of the equation (the reactants on the left, the products on the right).

To begin, this equation has:

1 Si

2 O

1 Ca

2 C  

on the left and

1 Si

1 Ca

3 O

1 C

on the right. Those numbers don't match!

By adding coefficients we end up with 5 Si, 10 O, 2 Ca and 4 C on both sides.