EXPERIMENT:
Determination of solubility product
ASSESSMENT CRITERIA: DCP, CE
Aim: To determine the solubility product of calcium hydroxide.
Theory: When a sparingly soluble salt is dissolved in water at a definite
temperature, equilibrium is established and the rate of dissolution of ions from
the solid equals to the rate of precipitation of ions from the saturated solution.
For example, when calcium hydroxide is dissolved in water, equilibrium exists
between solid Ca(OH)2 and the calcium and hydroxide ions present in the
saturated solution.
Ca(OH)2 = Ca2+ + 2OHRequirements:
Apparatus: Conical flasks (250ml) 6, filter funnels 3, beakers (100ml) 3, measuring
cylinder (100ml) 1, pipette (10ml) 1, burettes 2, burette stands 2.
Chemicals: Calcium hydroxide, hydrochloric acid, sodium carbonate, methyl
orange indicator.
Procedure:
Take about 2.0 grams of powdered calcium hydroxide in each of the three conical
flasks(250ml). Add 100ml of distilled water in each. Shake well and allow to stand
overnight.
Filter the solution into the beaker (250ml). Discard about 5 ml of filtrate in the
beginning because the filter paper absorbs solute until it attains equilibrium with
the solution. Take 10ml of the filtrate in a conical flask with the help of a pipette
and titrate it with standardized hydrochloric acid, using methyl orange as an
indicator. Repeat the same procedure for the other two solutions.
Preparation of Standard Hydrochloric Acid Solution
Prepare 0.1 M sodium carbonate solution by weighing 3.1g solid sodium
carbonate and dissolving it in distilled water and making it 250ml in a standard
flask. Prepare 250 ml of approximately 0.1 M hydrochloric acid. Now titrate
hydrochloric acid against the standard solution of sodium carbonate using methyl
orange as an indicator.
Record your observations and determine the solubility product of calcium
hydroxide.