A standard solution is a solution whose concentration is accurately and well known, that is a solution that contains a known mass of a solute dissolved in a known volume of Solvent.
For example, a solution that contains 22g of Sodium Chloride (NaCl) in 1dm3 of a solution is a Standard solution. A solution containing 3.2g of Potassium trioxocarbonate (IV) salt in 250cm3 of a solution of water is also a Standard solution.
In order to prepare a Standard solution in the laboratory, you must understand vividly the disparity or differences that exist between Molarity and Volume of a solution after it has been diluted.
Molarity according to Molar concept can be defined as the Moles of a solute per unit Volume of a solution when dissolved in 1dm3 of the solution. A concentrated solution is one that contains a large amount of solute dissolved in its solvent while a dilute solution is one that contains a small amount of the solute particles dissolved in its solvent. When water is used to dilute a concentrated solution, the concentration of the solution actually experience a decrease, but the amount or mole of the dilute solution remains the same with the amount or moles of the concentrated solution.
The number of moles
in Concentrated solution =======The
number of moles in dilute solution
That’s okay. Let’s move on. For any dilution of any concentrated solution, the relationship between the concentration and volume of the concentrated and dilute solution is
Before Dilution ======= After Dilution
Now having learnt the above, let’s have a simple problem;
1. Calculate the volume of 0.07mol/dm3 solution obtained when 200cm3 of 0.5 mol/dm tetraoxosulphate (VI) acid is diluted.
Concentration before Dilution
Volume before Dilution
Concentration after dilution
Volume after dilution——————–?
Therefore formularly, C1V1====C2V2
0.5 X 200 === 0.07 X V2
V2 ======= 0.5 x200 ÷ 0.07
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