Question

What is the difference between molar mass and atomic mass?

Answer 1

Molar mass is the mass of one mole of a substance.

Atomic mass is the mass of one individual unit of a substance.

An important concept regarding the mole is that
the atomic mass in `"amu"` of a substance is numerically equivalent to the mass in `"g"` of one mole of that substance.

To illustrate this fact, let's look at the compound sodium chloride (`"NaCl"`).

The atomic mass of `"NaCl"` can be found by using the atomic masses of the individual elements found on a periodic table:

`overbrace(22.99color(white)(l)"amu")^"sodium" + overbrace(35.45color(white)(l)"amu")^"chlorine" = overbrace(color(red)(ul(58.44color(white)(l)"amu")))^"sodium chloride"` `larr " atomic mass"`

This is numerically equivalent to the molar mass of `"NaCl"`. That is to say,

`overbrace(22.99color(white)(l)"g/mol")^"sodium" + overbrace(35.45color(white)(l)"g/mol")^"chlorine" = overbrace(color(red)(ul(58.44color(white)(l)"g/mol")))^"sodium chloride"` `larr " molar mass"`

So, the mass of one unit of `"NaCl"` is `58.44` `"amu"`, and the mass of one mole of `"NaCl"` is `58.44` `"grams"`.