The following strategies can be helpful for balancing certain
equations.
Strategy 1: Often, an element can be balanced by using
the subscript for this element on the left side of the arrow as the coefficient
in front of the formula containing this element on the right side of the arrow
and vice versa (using the subscript of this element on the right side of the
arrow as the coefficient in front of the formula containing this element on the
left side).
Strategy 2: It is sometimes easiest, as a temporary
measure, to balance the pure nonmetallic elements (H2, O2,
N2, F2, Cl2, Br2, I2, S8,
Se8, and P4 ) with a fractional coefficient (1/2, 3/2,
5/2, etc.). If you do use a fraction during the balancing process, you can
eliminate it later by multiplying each coefficient in the equation by the
fraction’s denominator (usually the number 2).
Strategy 3: If polyatomic ions do not change in the
reaction, and therefore appear in the same form on both sides of the chemical
equation, they can be balanced as if they were single atoms.
Strategy 4: If you find an element difficult to
balance, leave it for later.