Seema Saini Solutions for Chapter: Hydrogen, Water and Hydrogen Peroxide, Exercise 2: DPP

The bond energy of covalent $\mathrm{O}-\mathrm{H}$ bond in water is:

$1000 \mathrm{g}$ aqueous solution of ${\mathrm{CaCO}}_3$ contains $10 \mathrm{g}$ of calcium carbonate. The hardness of the solution is:

The pair that yields the same gaseous product on reaction with water is:

Hard water may be softened by using:

The presence of water can be inferred by:

The temporary hardness or carbonate hardness is due to the soluble $\mathrm{Ca}({\mathrm{HCO}}_3{)}_2$ and $\mathrm{Mg}({\mathrm{HCO}}_3{)}_2$ . The permanent non-carbonate hardness is due to ${\mathrm{CaCl}}_2, {\mathrm{MgCl}}_2, {\mathrm{CaSO}}_4$ and ${\mathrm{MgSO}}_4$. The process of removal of ${\mathrm{Ca}}^{2+}$ or ${\mathrm{Mg}}^{2+}$ ions is called softening of water.

Which is not present in clear hard water?`

The temporary hardness or carbonate hardness is due to presence of soluble $\mathrm{Ca}({\mathrm{HCO}}_3{)}_2$ and $\mathrm{Mg}({\mathrm{HCO}}_3{)}_2$. The permanent non-carbonate hardness is due to  ${\mathrm{CaCl}}_2, {\mathrm{MgCl}}_2, {\mathrm{CaSO}}_4$ and ${\mathrm{MgSO}}_4$. The process of the removal of ${\mathrm{Ca}}^{2+}$ or ${\mathrm{Mg}}^{2+}$ ions is called the softening of water.

A chemical $\mathrm{A}$ is used for softening to remove temporary hardness. $\mathrm{A}$ reacts with sodium carbonate to generate caustic soda. When ${\mathrm{CO}}_2$ is bubbled through a solution of $\mathrm{A}$, it turns cloudy. What is the chemical formula of $\mathrm{A}$?