Guide
1
Suppose you know that 500 ml of sulfuric acid solution contained 49 grams of the substance.Question: What is the molar concentration of this solution?Write down the exact formula of the substance - H2SO4, then calculate its molecular weight.It is the sum of the atomic masses of elements based on their indices.1 * 2 + 32 + 4 * 16 = 98 atomic mass units.
2
molar mass of any substance is numerically equal to its molecular weight, is only expressed in grams / mole.Therefore, one mole of sulfuric acid weighs 98 grams.How much is the initial number of moles of acid equal to 49 grams?Section:
49/98 = 0.5.
3
Consequently, 0.5 moles of sulfuric acid contained in 500 milliliters of solution.How many moles would be in 1 liter?Of course, one.So you One molar solution of sulfuric acid.Or, as they write, 1M solution.
4
And what is the normal concentration?This value showing how many equivalents of the substance (i.e., an amount of its moles is reacted with one mole of hydrogen) contained in one liter of solution.The dimension normal concentration - mol-eq / l or g-eq / l.It is denoted by the letters "N" or «N».
5
Consider an example with the same sulfuric acid.You've already figured out that her One molar solution.And 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 one another in equivalent ratios.Thus, the value of the normal sulfuric acid solution depends on a kind of reaction to what substance it enters.
6
example, H2SO4 + NaOH = NaHSO4 + H2O.In this reaction, for every molecule of sodium hydroxide as necessary, one molecule of sulfuric acid (or one equivalent of an alkali - one equivalent of acid).Therefore, in this case odnonormalny acid solution (1N, or just N).
7
alkali But if taken in excess, the reaction will flow as follows: H2SO4 + 2NaOH = Na2SO4 + 2H2O.Then, as for each acid molecule, two molecules have already alkali, the solution is dvuhnormalnym acid (2N).