The mass fraction of solution is a chemical term which can be useful at the solution of tasks during control or independent work and also when performing a settlement part of practical tasks. However it is not necessary to think that if gold school hours are finished, then more this knowledge will not be useful. First, the younger generation can approach the parent with a question on this subject. And secondly, calculation of a mass fraction can be necessary, for example, for definition of concentration of medicinal or food solutions (vinegar). It is not less important to apply knowledge when calculating amount of fertilizers.

## It is required to you

- Handle, paper, calculator

## Instruction

1. The mass fraction is the relation of mass of the dissolved substance to the mass of solution. And it can be measured or as a percentage, then for this purpose the received result needs to be increased by 100% or in mass fractions (in this case has no units of measure). Any solution consists of solvent (water – the most widespread solvent) and the dissolved substance. For example, in any solution of salt water will be solvent, and salt will act as the dissolved substance. For calculations it is necessary to know at least two parameters – the mass of water and mass of salt. It will give the chance to calculate a mass fraction of substance in solution which is designated by letter w (omega).

2. Example 1. The mass of solution of potassium hydroxide (KOH) of 150 g, mass of the dissolved substance (KOH) of 20 g. Find a mass fraction of alkali (KOH) in the received solution.m (KOH) = 20 gm (KOH) = 100 gw (KOH)-? There is a formula by which it is possible to determine a mass fraction of substance.w (KOH) = by m (KOH)/m (solution (KOH) x 100%teper calculate a mass fraction of the dissolved substance of potassium hydroxide (KOH): w (KOH) = 20 g / 120 g x 100% = 16.6%

3. Example 2. The mass of water is 100 g, the mass of table salt is 20 g. Find a mass fraction of chloride of sodium in solution.m (NaCl) = 20 gm (waters) = 100 gw (NaCl)-? There is a formula by which it is possible to determine a mass fraction of substance.w (NaCl) = by m (NaCl)/m (NaCl solution) x 100%prezhde what to use this formula, find the mass of solution which consists of the mass of the dissolved substance and mass of water. Therefore: m (NaCl solution) = + m (water) Substitute m (the dissolved substance NaCl) concrete znacheniyam (NaCl solution) = 100 + 20 = 120 gteper calculate a mass fraction of the dissolved substance: w (NaCl) = 20 g / 120 g x 100% = 16.7%