I'm not sure. I have a glass of 450 milliliter solvent. In this solvent are 5.40 g NaOH. The concentration is 0.300 mol / g. Are the 450 milliliters the volume of the solvent alone, or is it the volume of the solvent when NaOH is already present? And if it’s both, how can I find out the volume only of the solvent?
Thanks for your anwsers 

Water is solvent.

Water + dissolved NaOH is solution.

Mass of solvent and mass of dissolved substance add together in solution (quantum scale of mass is lost or gained if reaction is exothermic/exoenergetic or endothermic/endoenergetic).

With volume it is no so simple.

 

Edited December 9, 20187 yr by Sensei

1 hour ago, KlausZahn said:

The concentration is 0.300 mol / g

No.

That's impossible. a mole of sodium hydroxide is about 40 grams so 0.3 moles is about 12 grams.

 

There are tables of densities of solutions which might help answer your question.