100 mL of a water sample contains 0.81g of calcium bicarbonate and 0.73g of magnesium bicarbonate. The hardness of this water sample expressed in terms of equivalent of `CaCo_3` is `10^x` ppm. What is numerical value of x? (molar mass of calcium bicarbonate is `162 gmol^(-1)` and magnesium bicarbonate is `146g mol^(-1))`

Answer

3

Explanation

`g_(Ca(HCO_3)_(2))=0.81,n(HCO_(3))_2=(0.81)/(162)=1/200,g_(Mg(HCO_3))_(2)=0.73g,n_(Mg_(HCO_3))_(2)=1/200`
`n_(T)=1/200+1/200=0.01`
0.01 moles in 100 ml water
`(0.01xx2)` equivalent in 100 ml water `:.` 0.02 equivalent of `CaCO_3` in 100 ml water
`:.` 0.01" moles of `CaCO_3` in 100 ml water
`0.01xx100g " of " CaCO_3`
Hardness `implies 1/100L xx10^(3)mg xx1000=10,000` ppm.