Determination of Mineral Acidity and Total Acidity in Water

Aim

To determine the mineral acidity and total acidity of the given water sample.

Apparatus

Burette, pipette, conical flask, measuring jar.

Reagents

  1. 02 N Sodium hydroxide (0.02 N NaOH)
  2. Methyl orange indicator
  3. Phenolphthalein indicator
  4. Sodium thio sulphate 0.1 N

Theory

Acidity of a solution is a measure of its capacity to neutralize bases. Acidity is caused  due to the presence of mineral acids (Al2(S04)3, Fe2SO4), CO2, strong acids and weak bases. This is caused mainly due to industrial wastes. Acidity of a sample is determined by titrating against a strong solution of a base (alkali) such as NaOH. Types of Acidity include Mineral acidity (partial acidity) and Total acidity.

Procedure

Mineral Acidity

  1. Pipette out 25ml of the given water sample into a  clean conical flask. Add  3 drops of methyl orange indicator to it. The solution becomes pink in colour.
  2. Titrate this solution against 0.02 N NaOH solution taken in the burette till the colour changes from pink to pale yellow.
  3. Note down the burette reading which indicates the volume of Na OH run down (consumed). Repeat the experiment until at least 2 concurrent readings are obtained
  4. The end point is pink to yellow pale
Trial NoInitial ReadingFinal readingDifference
1
2
3
4

Calculation 
The End Point is Pink to pale Observation

Where,

P = [A × N × 50 × 1000] / ml of sample =                    mg/l as CaCO3 A = Volume of NaOH consumed.

N = Normality of NaOH (0.02)

Result:

Procedure

Total Acidity

  1. Pipette out 25ml of the given water sample into a clean conical flask.
  2. Add 3 drops of phenolphthalein indicator to it. The solution becomes colorless.
  3. Titrate this solution against 0.02 N NaOH solution taken in the burette till the colour changes to pink.
  4. Note down the burette reading which indicates the volume of NaOH run down (consumed).
  5. The End Point is Colorless to pink.
  6. Repeat the experiment until at least 2 concurrent readings are obtained

Observations

Trial NoInitial ReadingFinal readingDifference
1
2
3
4

Calculation

T = [B ×N × 50 × 1000] / ml of sample=                    mg/l as CaCO3 Where,

B = Volume of NaOH consumed.

N = Normality of NaOH (0.02)

Result:

 

Total
0
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