How to calculate concentration

How to calculate concentration

Meets a concept of concentration of people not only in the fields of science, but also in everyday life. For example, the mass fraction of fat specified on food (milk, oil, etc.) nothing but percentage concentration. Except it there are still molar, normal and molal concentration. And it is easy to calculate any of them on formulas.

It is required to you

  • - handle;
  • - paper;
  • - periodic table;
  • - calculator.


1. To find a mass fraction (percentage concentration) of any given substance, divide its weight into the lump of solution (mix). Receive result in unit shares which then you can convert into percent that too will be true. For example, the task is given: for preparation of solution took 150 g of water and 50 g of sugar. It is necessary to calculate percentage concentration of the dissolved substance. For the decision at first write down a formula, and then find required size: ω (sugar) = m (sugar)/m (solution) = 50/(150+50) =0.25 * 100% = 25%B solution 25% of sugar contain.

2. At calculation of molar concentration, you have to divide amount of substance into the total volume of solution. The mol/l will be unit of measure, in this case. The formula for calculation has the following appearance: C = n (the dissolved substance) / V, gdes – molar concentration (mol/l); n – amount of substance (mol); V – total volume of mix (liter).

3. Normal concentration is expressed in a gram equivalent/litre and designates quantity of equivalents of a certain substance in 1 l of solution which is equal, at chemical reactions, 1 g of hydrogen or 8 g of oxygen. Let's allow to you it is necessary to calculate normality of 70% of sulfuric acid which density is equal to 1.615 g/l. From a statement of the problem it is clear that 100 g of solution contain 70 g of acid. Therefore at first find the volume of this solution: V = 100/1.615 = 61.92 (ml). Then calculate the mass of H2SO4 acid is bibasic: Sn = m*z/M =1130.49*2/98 = 23.06 N.

4. If you need to calculate molal concentration of solution (molyalnost) – use the following formula: The cm = n/m, gdesm – molal concentration is measured in mol/kg; n – amount of a certain substance in moths; m – total mass of solution in kilograms. Unlike molarity the molal concentration does not depend on temperature conditions of course of reaction.

Author: «MirrorInfo» Dream Team