What is the formula for calculating the number of moles from grams?

The formula for calculating the number of moles from grams is rooted in the relationship defined by the molar mass of a substance. Molar mass, which is the mass of one mole of a substance (usually expressed in grams per mole), serves as the conversion factor between grams and moles.

When you divide the mass of the substance in grams by its molar mass, you are essentially determining how many times the mass of one mole fits into the total mass you have. This provides the amount of substance in terms of moles.

For example, if you have 18 grams of water and the molar mass of water (H2O) is approximately 18 g/mol, using the formula:

Moles = grams / molar mass,

you would calculate ( 18 \text{ grams} / 18 \text{ g/mol} = 1 \text{ mole} ).

This clear relationship makes the formula not only correct but fundamental in analytical chemistry for converting between mass and moles, an essential step in many calculations and analyses.