A hard water sample contains dissolved `Mg(HCO_3)_2` only. If degree of hardness of that sample is 150ppm, calculate the weight of `Mg(HCO_3)_2` present in 1kg of water sample.

Explanation

Degree of hardness is 150ppm. It means that `10^6`g of water sample contains 150 g of `CaCO_3` (which is equivalent to `Mg(HCO_3)_2` .
Weight of `CaCO_3` in 1kg `(10^3 g)` of water
`= (10^3 xx 150)/(10^6) =0.15 g `
0.15 g of `CaCO_3 -= 0.219 g ` of `Mg(HCO_3)_2`
0.15 g of `CaCO_3 -= (146 xx 0.15)/(100)`
`= 0.219g Mg (HCO_3)_2`
Weight of `Mg(HCO_3)_2` present in 1kg of water = 0.219 gram