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• textbook on analytical and general chemistry of any author.
Guide
1
It should be noted that the composition of the solution (or the content of the solute in solution) can be expressed in many ways: the dimensional and dimensionless quantities.Dimensionless quantity (shares, interests) do not apply to concentrations, asconcentration - the value dimension.In chemistry mainly use 3 types of concentration: the molar concentration or molarity, or molality molal concentration and equivalent or normal concentration.
molar or molarity concentration - the ratio of the volume of the substance to the solution.See calculated by the formula = n / V, where n - amount
of substance in mol, V - the volume of solution L.Also, this concentration may indicate the letter M after the number.For example, the recording means 5 M HCl that CM (HCl) = 5 mol / l, i.e.5 moles of HCl are in 1 liter of water.Note: If the problem is not specified the amount of substance, but its mass is listed, you can use the formula n = m / Mr, where m - mass of matter, g, Mr - molecular weight (can be calculated using the table Medeleeva DI)n - amount of substance in mol.This concentration is changed by increasing or decreasing temperature.
2
molal concentration molality or - the ratio of the amount of substance to the weight of the solvent.Is calculated according to the formula m = n / M (solution), where n - amount of substance in mol, M (solution) - weight of the solution in kg.For example, m (HCl) = 5 mol / kg (H2O), means that 1 kg of water accounts for 5 mol HCl.The solvent is not necessarily the water (depending on the conditions of the problem), we can calculate the amount of the substance (method specified in the first paragraph), at molal concentration does not change.
3
equivalent or normal concentration - the ratio of equivalents of solute to the volume of solution.Means normal concentration can be removed and the letter n.after the number.For example, 3N.HCl - means a solution in which each liter is 3 equivalents of hydrochloric acid.The calculation of the equivalent - a separate issue, which if necessary can be found in school textbooks in chemistry.This concentration is frequently used in analytical chemistry, where it is necessary to know in which volume ratios of mixed solutions: solute should react evenly, i.e.C1 C2 = V1 * V2 *, where C1 and V1 - Concentration and volume of solution, and C2 and V2 - the concentration and amount of the other solution.Using these kinds of concentrations, it is possible to solve the problem.