The amount of a substance (matter quantity) is expressed in moles (mol)
How to calculate the amount of a chemical substance ?
Mass concentration of an aqueous solution
concentration in matter quantity of an aqueous solution
Mass of a substance
Volume of gas
Density
The mass concentration c is expressed in gramms per liter (g/L), it is the mass of solute in one liter of solution.
For ideal gases (gases where we can consider molecules as point that do not interfer wth each other), the molar volume is equal to 25 L/mol (at T=20°C and p=1 bar). This is a good approximation for many common gases at standard temperature and pressure. This represents the volume occupied by 1 mol of gas.
Mass of a substance
M represents the molar mass in g/mol which is the mass of 1 mole of a substance. Example : M(O) = 16 g/ mol which means 1 mole of Oxygen weighs 16 g. For a molecule you must add the atomic molar mass.
Density
The volumetric mass ρ of a solution is the mass of a solution per liter of solution (g/L). The density d has no unit it is the volumetric mass divided by the volumetric mass of water which is equal to 1g/mL. So if you have the value of the density you have the volue of the volumetric mass in g/mL.
Concentration in matter quantity of aqueous solution
The molar concentration of a solute in a solution C is given in mol/L. It is the amount of substance per liter of solution.