# Gram Formula Mass

The gram formula mass of a compound is the amount of that compound that has the same mass in grams as the formula mass in atomic mass unit. An atom of each element has a characteristic mass and in like manner each molecule of a compound has a characteristic formula mass.

When the formula mass of an ionic compound is determined by the addition of its component atomic masses and expressed in grams, it is called the **Gram Formula Mass****. **

**Gram Formula Mass** is mathematically expressed as

The gram formula mass of a substance is the sum of the atomic masses of all atoms is a formula unit of the compound, whether molecular or not.

**
**

1 K = 39

1 Al = 27

2(SO

12 H

1 Ca = 40

1 C = 12

3 O = 48 = 3 $\times$ 16

## Gram Formula Mass Problems

Solved problems based on gram formula mass are given below.

### Solved Examples

**Question 1:**Find the gram formula mass of 1mol of KAl(SO

_{4})

_{2}.12H

_{2}O?

**Solution:**

1 K = 39

1 Al = 27

2(SO

_{4}) = 192 = 2(32 + 16 $\times$ 4)

12 H

_{2}O = 216 = 12(2 + 16)

Therefore the gram formula mass is

1 mol = 474g

**Question 2:**Find the gram formula mass of 1mole of CaCO

_{3}?

**Solution:**

1 Ca = 40

1 C = 12

3 O = 48 = 3 $\times$ 16

Therefore the gram formula mass of CaCO_{3} is

CaCO_{3} = 100 formula mass

CaCO_{3} = 100g = gram formula weight.