For example, did you know that in 500 milliliters of a solution of sulphuric acid contains 49 grams of this substance. Question: what is the molar concentration of this solution? Write down the exact formula of a substance h 2 so 4, and then calculate its molecular mass. It is the sum of the atomic masses of the elements given their indices. 1*2 + 32 + 4*16 = 98 atomic mass units.
The molar mass of any substance is numerically equal to its molecular weight, only expressed in grams/mol. Therefore, one mole of sulfuric acid weighs 98 grams. How many moles is the initial amount of acid, equal to 49 grams? Divide: 49/98 = 0.5 in.
Therefore, 0.5 moles of sulfuric acid are contained in 500 milliliters of solution. How many moles would be in 1 liter? Of course, one. So, you odnokolernyh solution of sulfuric acid. Or, as usually written, 1M solution.
And what is the normal concentration? This value shows how many equivalents of a substance (the number of moles of that reacts with one mole of hydrogen) contained in one liter of solution. The dimension of the normal concentration - mol-EQ/l or EQ/L. It is denoted by the letters "n" or "N".
Consider an example with the same sulfuric acid. You already figured out that her solution odnokolernyh. What will be its normal concentration? To answer this question you need to consider that according to the law of equivalents, all substances react with each other in equivalent proportions. Thus, the value of normality of the sulfuric acid solution depends on what kind of reaction what kind of substance it is to join.
For example, H2SO4 + NaOH = nahso4 solution + H2O. In this reaction, for each molecule of sodium hydroxide has also one molecule of sulfuric acid (or equivalent alkali is one equivalent of the acid). Therefore, in this case, the acid solution adnormality (1N or just N).
But if the alkali is taken in excess, the reaction will proceed like this: H2SO4 + 2NaOH = Na2SO4 + 2H2O. Then, since each molecule of acid has two molecules of alkali, the acid solution will dvuhseriynyy (2N).