`0.0093 g of Na_(2)H_(2)EDTA.2H_(2)O` is dissolved in `250 mL` of aqueous solution. A sample of hard water containing `Ca^(2+)` and `Mg^(2+)` ions is titrated with the above `EDTA` solution using a buffer of `NH_(4)OH+NH_(4)Cl` using eriochrome balck-`T` as indicator. `10 mL` of the above `EDTA` solution requires `10 mL` of hard water at equivalent point. another sample of hard water is titrated with `10 mL` of above `EDTA` solution using `KOH` solution `(pH=12)`. using murexide indicator, it requires `40 mL` of hard water at equivalence point.
a. Calculate the ammount of `Ca^(2+)` and `Mg^(2+)` present in `1L` of hard water.
b. Calculate the hardness due to `Ca^(2+)`, `mG^(2+)` ions and the total hardness of water in p p m of `CaCO_(3)`. (Given MW(EDTA sal t)=372 g `mol^(-1),MW(CaCO_(3))=100 gmol^(-1)`)

Explanation

To solve the problem step-by-step, we will break it down into parts (a) and (b) as per the question.

### Part (a): Calculate the amount of Ca²⁺ and Mg²⁺ present in 1L of hard water.

1. **Calculate the Molarity of EDTA Solution:**
- Given: Mass of Na₂H₂EDTA·2H₂O = 0.0093 g
- Molecular weight of EDTA salt = 372 g/mol
- Volume of solution = 250 mL = 0.250 L
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