The concentration of a solution

The concentration of a solution is an indication of how much solute there is dissolved into the solvent. There are a number of ways to express concentration of a solution. By far the most used and the most useful of the units of concentration is molarity. You might see 6 M HCl on a reagent bottle. The M is the symbol for molar. One molar is one mol of solute per liter of solution. The reagent bottle has six mols of HCl per liter of acid solution. Since the unit molar rarely appears in the math of chemistry other than as a concentration, to do the unit analysis correctly, you will have to insert concentrations into the math as mols per liter and change answers of mols per liter into molar .
Molality is concentration in mols of solute per kilogram of solvent. Mol fraction is the number of mols of solute per number of mols of solution. Weight-weight percent (really mass percent) is the number of grams of solute per grams of solution expressed in the form of a percent. Mass-volume concentration is the number of grams of solute per milliliter of solution. There are other older units of concentration, such as Baume (or Baumé), that are still in use, mainly in industrial chemicals .
Normality is the number of mols of effective material per liter. In acid-base titrations, the hydroxide ion of bases and the hydrogen (hydronium) ion of acids is the effective material. Sulfuric acid (H2SO4) has two ionizable hydrogens per formula of acid, or one mol of acid has two mols of ionizable hydrogen. 0.6 M H2SO4 is the same concentration as 1.2 N H2SO4