easiest option determine the concentration of interest - when you know the initial mass of dry matter, subsequently dissolved.Assume initially had 15 grams of some salts.Then it is completely dissolved in water.We need to calculate the percentage concentration .
first weigh the container with a solution.For example, you will have 800 grams.Then pour the solution and weigh the empty container.Suppose it weighs 550 grams.A further object is simple: 15 / (800 - 550) = 0.06, or 6%.Here is the concentration of the solution .
little complicate the task.Take 20 grams of salt (sodium chloride), and dissolve it in a certain amount of water.Then, the overflow solution in a graduated cylinder and carefully add water, bring the volume to 200 milliliters.Wha
t is the percentage concentration of the resulting solution ?
It would seem that the task - simply nowhere.The density of water is one, therefore, 200 ml - 200 grams, and the percentage concentration will be 20/200 = 0.1, or 10%.But do not rush to conclusions.After all, you do not have 200 milliliters of pure water and 200 milliliters of solution , the density of which is different from the unit.
So you, as in the above case, it is necessary to know the total weight of the solution M, initially weighing vessel with him, and then - an empty vessel.Then, section 20 (a lot of salt) on M, and multiplying the result by 100%, you will get the answer.
Well, if you for some reason it is not possible either to weigh or measure the amount?How, then, to determine the concentration of interest solution ?For example, there is a certain amount of water solution of sulfuric acid - a well-known substance.Before you set a goal - to calculate its interest concentration , without using any weights or measuring utensils.
At first glance, a very difficult task.And in fact, solve it - a piece of cake.The fact is that almost any substance which is used in various industries, there are so-called "table of densities solution ».But sulfuric acid - the substance is so widely used that to find a table for it is not difficult.It is the most reference books on chemistry.
First of all, you need to measure the density of sulfuric acid with a device called "densitometer" (in other words it can be called "densitometer").Suppose the obtained value is equal to 1.303 gram / milliliter.In the table, determine the density: a solution which corresponds to the percentage concentration of this value.This 40% solution of sulfuric acid.The problem is solved.