50ml standard hard water (1.2gm CaCO3/L) requires 32ml of EDTA solution.

Answer to :

50ml standard hard water (1.2gm CaCO3/L) requires 32ml of EDTA solution. 100ml of water sample consumes 14ml of EDTA solution. 100ml of boiled water takes 8.5ml of EDTA. Find temporary and non-carbonate hardness of water sample.

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Temporary hardness ≈ 103.1 ppm; non-carbonate (permanent) hardness ≈ 159.4 ppm (total hardness 262.5 ppm).

Step 1: Standardise EDTA. Standard hard water has 1.2 g/L = 1200 mg/L CaCO₃, so 50 mL contains

\[\frac{1200 \times 50}{1000} = 60\ \text{mg CaCO}_3\]

This needs 32 mL EDTA, so

\[1\ \text{mL EDTA} = \frac{60}{32} = 1.875\ \text{mg CaCO}_3\]

Step 2: Total hardness. 100 mL sample uses 14 mL EDTA:

\[14 \times 1.875 = 26.25\ \text{mg in 100 mL}\]

\[\text{Total} = 26.25 \times 10 = 262.5\ \text{ppm}\]

Step 3: Permanent (non-carbonate) hardness. Boiling removes temporary hardness; 100 mL boiled water uses 8.5 mL:

\[8.5 \times 1.875 = 15.94\ \text{mg in 100 mL}\]

\[\text{Permanent} = 159.4\ \text{ppm}\]

Step 4: Temporary (carbonate) hardness

\[262.5 - 159.4 = 103.1\ \text{ppm}\]

(ppm here means mg of CaCO₃ equivalent per litre.)