In which of the following equations does ${\mathrm{H}}_2{\mathrm{O}}_2$ act as a reducing agent in the acidic medium?

By which reason temporary and permanent hardness occur?

Define two method by which we can soften the water sample.

Which of the following orders are correct ?

(a) ${\mathrm{TiH}}_2<{\mathrm{BeH}}_2<{\mathrm{CaH}}_2$ -Electrical conductance

(b) $\mathrm{LiH}<\mathrm{NaH}<{\mathrm{CaH}}_2$ -Ionic character

(c) $\mathrm{F}-\mathrm{F}<\mathrm{H}-\mathrm{H}<\mathrm{D}-\mathrm{D}$ -Bond dissociation enthalpy

(d) ${\mathrm{H}}_2\mathrm{O}<{\mathrm{MgH}}_2<\mathrm{NaH}$-Reducing character