Equivalent Weight and Mole Ratio

EQUIVALENT WEIGHT AND MOLE RATIO

The equivalent weight or gram equivalent is the mass of a given substance that will combine with a fixed quantity of another substance. The equivalent weight of a specific element is the mass of the element that will combine with 1.008 grams of hydrogen or 8.0 grams of oxygen or 35.5 grams of chlorine. It can also be determined by an elements atomic weight divided by its valence number.

Molar ratio is the ratio of two molecules in a chemical reaction. For example, the equation 2 moles of H2 gas plus one mole of O2 gas goes to 2 H2O molecules is a balanced equation, which leads to a molar ratio of 1:2 between oxygen and H2O because it takes one O2 molecules to make 2 H2O molecules in the balanced equation. The ratio for hydrogen and H2O is 1:1 because they both have equal mole numbers on opposite sides of the equation.

The equation ozone or O3 going to oxygen O2 is completely unbalanced as it is because that would leave an extra Oxygen atom left over in the equation. You cannot calculate the mole ratio in an unbalanced equation. But if you balance it you get 2 moles of O3 going to 3 moles of O2 with a mole ratio of 2:3.