Question

How is molarity related to concentration?

Answer 1

In a one-sided way.

Molarity (units of `"M"`) is a type of concentration, and concentration isn't necessarily molarity.

`"M" = "mol solute"/"L solution"`,

whereas concentration is in general in units of any of the following:

• `"things"/"volume"`
  (number concentration, such as number of particles in a certain volume)

• `"mass"/"volume"`
  (density, or mass concentration)

• `"mol solute"/"L solution"`
  (molality, or molar density)

• `"L of i"/"total L"`
  (volume concentration, which I've never heard of, but it exists...)

• `"mass of i"/"total mass"`
  (mass fraction, or parts per...; i.e. `"xg"/"yg"`, where `x` and `y` are prefixes such that the concentration is not numerically gigantic)

• `"mol solute"/"kg solvent"`
  (molality)

• `"mols of i"/"total mols"`
  (mol fraction)

• `"mols of i"/"mols of j"`
  (mol ratio)

So clearly, there is more than just molarity when it comes to concentrations.