Percentage concentration of solution is the size showing the attitude of mass of the dissolved substance to solution lump. In other words, it is the mass fraction of substance in solution expressed as a percentage.

## Instruction

1. The simplest option of definition of percentage concentration – when the initial mass of solid, subsequently dissolved is known to you. Let's assume, initially there were 15 grams of some salt. Then it was completely dissolved in water. It is required to calculate percentage concentration.

2. At first weigh the container with solution. For example, you will have 800 grams. Then pour solution and weigh empty capacity. Let's assume, it weighs 550 grams. And further the problem is solved elementary: 15/(800 – 550) = 0.06, or 6%. Here such is concentration of solution.

3. Let's a little complicate a task. Take 20 grams of table salt (sodium chloride) and dissolve it in a number of water. Then, having poured solution in a measured cylinder and carefully adding water, bring volume to 200 milliliters. What percentage concentration of the received solution?

4. It would seem, the task – is no place more simply. Density of water is equal 1, therefore, in 200 milliliters – 200 grams, and percentage concentration will be 20/200 = 0.1, or 10%. But you do not hurry with conclusions. You have not 200 pure milliliters, but 200 milliliters of solution which density differs from unit.

5. Therefore to you as in the above case, it is necessary to learn solution M lump, at first having weighed a vessel with it, and then – an empty vessel. And then, having divided 20 (the mass of salt) into M, and having increased result by 100%, you receive the answer.

6. Well, and if you for some reason have no opportunity neither to weigh, nor to measure volume? How then to define percentage concentration of solution? Here, for example, there is some amount of water solution of sulfuric acid – well-known substance. The task – to calculate its percentage concentration is set for you, without using either scales, or measured ware.

7. At first sight task very difficult. And actually to solve it – a piece of cake. The fact is that practically for any substance finding application in various industries there are so-called "tables of density of solution". And sulfuric acid – so widely applied substance that to find such table for it does not represent work. It is in the majority of reference books on chemistry.

8. First of all you need to measure density of sulfuric acid by means of the device under the name "densitometer" (in a different way it can be called "densitometer"). Let's assume, the received size is equal 1.303 grams / a milliliter. Determine by the table of density: to what solution of percentage concentration there corresponds this size. It is 40% solution of sulfuric acid. The task is solved.