# Question #1148f

##### 2 Answers

No they are not..

#### Explanation:

**Formula mass** is the sum of the atomic weights in atomic mass units of the substance formula.

**Molar mass** is also sum of the atomic weights in

Formula mass unit →

Molar mass unit →

No, formula mass and molar mass are **not** the same thing.

#### Explanation:

**Formula mass**

The **formula mass** of a substance is the sum of the average atomic masses of all the atoms represented in the substance’s formula.

For example, the formula for water is

The average atomic mass of an

Thus, the formula mass of water is

Similarly, the formula for hydrogen peroxide is

Its formula mass is

The units for formula mass are **unified atomic mass units**, with symbol **u**.

**Molar mass**

The molar mass **mole** (

The SI base unit for molar mass is kilograms per mole (kg/mol).

However, for historical reasons, molar masses are almost always expressed in grams per mole (g/mol).

The mole is defined so that the molar mass of a substance in grams per mole is **numerically** the same as the formula mass in unified atomic mass units.

Thus, the formula mass of water is 18.02 u, so the molar mass of water is 18.02 g/mol.