# How to find concentration?

This concentration, known to us from childhood, determines the amount of a substance in any solution. And most often the task of how to find the concentration is used in such science as chemistry, mainly in various experiments. Because it is very important that the necessary solution is properly prepared, because a lot will depend on it.

In addition to chemistry, how to find the concentration of the solution is used in other scientific fields, and is often used by humans and in everyday life when preparing an exact solution of sugar, salt or soda, for example.

## Types of concentrations and formulas

If we talk about chemistry, then there are mainly used three main types of concentrations. This is usually a molar or (molarity) concentration, followed by a molar (molality), and also an equivalent or normal concentration should be added here.

- As for the first (molar) concentration, it is the ratio of the total amount of the solute to the volume of the solution:
Cm = n / v

Symbols:

- n is the amount of the whole substance, mol,
- V is the volume of the solution itself, l.

Another such concentration, as a rule, is designated by the letter M. In the event that M stands after the number 5, then it is 5 mol / l.

- In terms of molal concentration or molality, this is the ratio of the amount
substances to the mass of the solvent itself:

m = n / M (solution)

Here:

- n is the amount of substance, mol,
- M is the mass of the solution.

- Another type of concentration is called - equivalent, or (normal) concentration - the ratio of the number of equivalents of the substance that we dissolve, to the volume of the solution itself. It is denoted by: СН or by the letter числа after the number (3 nСl - in the liter of the p-ra - 3 equivalents of the substance).

## Problem solving

### Example 1

1 kg of salt is dissolved in 9 liters of pure water. Question: how to find the concentration of the solution and what it will be equal to? (the mass of 1 liter of water is 1 kg).

Decision:

We know that the mass of the substance that is dissolved (in this case, salt) is 1 kilogram. The mass of water in the solution is 9 kilograms. Thus, up to 9 kg +1 kg, you get 10 kilograms, will be the total weight of the solution.

1/10 = 0,1 = 10%

As a result, we get a 10 percent concentration of the solution.

### Example 2

Calculate the normality and molarity of 70% H solution2SO4, i.e.how to find the concentration of a substance (r = 1.615 g / ml).

Decision:

It is necessary to calculate the mass H2SO4in 1 liter of the prepared solution. 70% H2SO4 contains 70 g of H2SO4 in 100 g of the p-ra.