CONCENTRATION OF SOLUTIONS

SOLUTION: Solute and solvent

Solute: substance in smaller quantity; can be solid liquid or gas.

Solvent is in larger quantity; can be solid, liquid or gas.

Amount of solute per unit volume of solvent is called CONCENTRATION.

There are calculations of amount of substance CONCENTRATION in different ways.

MOLARITY: moles of solute per liter of solvent

Normality is related to number of positive ions in acidic or ionic solution per unit volume of solvent. This is related to the Molarity =n[Normality], where n = number of positive ions in the solution.

E.g. 1 Molar HCl = 1 normal HCl, but 1 molar H₂SO₄ = 2 Normal H₂SO₄

MASS CONCENTRATION = mass in grams of solute per liter of solute. This is also called density of solution.

% solution= amount of solute (moles or mass) per total mass of solution x 100.

Mass of solution = mass of solute + solvent.

Parts per million(ppm) = one part (gram or mole) solute per million parts (grams or moles) of solvent.

MOLALITY = moles of solute per kilogram of solvent.

DILUTIONS

Adding more solvent to solution. Amount of solute remains constant but solution concentration decreases.

Concentration = moles / volume                                                           Moles = concentration x volume.

Moles[original]=moles[dilute]

C[original] x V[original] = C[dil] x V [dil]                                                   V [dil]= V[original] + V[added solvent]

C[dil] = C[original] x V[original]/ V [dil]

The ratio: V[dil]/V[original] is called Dilution factor. This is the same as ratio of C[original]/C[dil]