Mol/Dm3 or G/Dm3?

In my GCSE revision guide, it says that the concentration of something is the mass/volume... but when doing titrations, the formula to find the concentration can also be number of moles/volume.

Which formula should I use: Mass/Volume, or Moles/Volume?
Thank you 😃

You can use both it depends what information you are given in the question

Both are valid forms, usually concentration will be given in mole/volume.
If you need to change between moles and mass just use Mass = Mr * Mole

In the revision guide, it's explaining the general principle. If you were describing the 'concentration' of sugar in your tea, you'd talk about the 'amount' of sugar you'd put in the cup. And you'd ordinarily describe 'amount' in terms of mass - thus, mass/volume is a way of describing concentration.

Being more scientific about it, 'mass' doesn't properly describe 'amount of substance', because different atoms have a different mass, relative to one another. As you know, 'amount of substance' is properly masured in moles, and thus concentration is moles/volume. You'll see this written differently as mol.dm^-3, mol/dm³, mol/L, mol.L^-1, 'M'...