Chapter 21.5, Problem 1Q

Interpretation Introduction

Interpretation: the mass of $CaO$ required to precipitate $M{g}^{2+}$ and $C{a}^{2+}$, the total mass precipitate $CaC{O}_3$ and $MgC{O}_3$ are needed to be determined for the given sample of hard water.

Concept introduction:

The equation relating number of moles and given mass is,

$\text{Number of moles}\text{=}\frac{\text{Given}\text{mass}}{\text{Molecular}\text{mass}}$

Equation for Mass of a substance from its number of moles is,

$\text{Number of moles}\text{×}\text{Molecular}\text{mass in grams}\text{=}\text{Number}\text{of}\text{grams}$

The reactions occurs while treating hard water with $CaO$ is,

$C{a}^{2+}+2HC{O}_3{}^{-}+CaO\to 2CaC{O}_3+H_{2}O$

$M{g}^{2+}+2HC{O}_3{}^{-}+CaO\to CaC{O}_3+MgC{O}_3+H_{2}O$