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# How to calculate the molar concentration

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What is the molar concentration? This is a quantity that indicates how many moles of a substance are in one liter of solution.

The method for finding the molar mass depends on the conditions of the problem.

You will need

• - accurate scales-
• - dimensional capacitance-
• - salt solubility table-
• - Periodic table.

Instructions

1

For example, you are asked to determine what the molar concentration of the solution is 71 grams of sodium sulfate contained in 450 milliliters of the solution.

2

First of all, write the exact formula of sulphateSodium: Na2SO4. Write out the atomic weights of all the elements that make up the molecule of this substance: Na-23, S-32, O -16. The total atomic weights are as follows: Na-46, S-32, O-64. Consequently, the molecular weight of sodium sulfate is 142.

3

Dividing the actual weight of sodium sulfate by molar, find out how many moles of this salt is contained in the solution. This is done as follows: 71/142 = 0.5 mol.

4

If 71 grams of sodium sulfate were contained in1000 ml of solution, it would be 0.5 molar solution. But you have 450 milliliters, therefore, you need to do the recalculation: 0.5 * 1000/450 = 1,111 or roundly 1.1 molar solution. The problem is solved.

5

Well, and if you were given (say, on a laboratoryA chemistry workshop) an unknown amount of a substance, for example sodium chloride, a container with an unknown amount of water, and proposed to determine the molar Concentration Solution that has not yet been obtained? And here there is nothing difficult.

6

Thoroughly weigh sodium chloride, preferably on accurate (laboratory, ideally - analytical) scales. Write down or remember the result.

7

Pour water into a measuring container (laboratory graduated glass or graduated cylinder), set its volume, and, accordingly, the mass, since the water density is equal to 1.

8

Make sure, using the salt solubility table, that all sodium chloride will dissolve at this room temperature in such an amount of water.

9

Dissolve the salt in water and again, using a measuring container, set the exact volume of the solution obtained. Calculate the molar Concentration Solution according to the formula: m * 1000 / (M * V), where m is the actual mass of sodium chloride, M is its molar mass (about 58.5), and V is the volume of the solution in milliliters.

10

For example, the mass of sodium chloride was 12 grams, the volume of the solution was 270 ml.12000 / (58.5 * 270) = 0.7597. (Approximately 0.76 molar solution).

How to calculate the molar concentration Was last modified: June 21st, 2017 By
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