c
Reaction with \(HCl\)

\(Ca ( OH )_2+2 HCl \rightarrow CaCl _2+2 H _2 O\)

Volume of \(Ca ( OH )_2=10 ml\)

Volume of \(HCl =20 ml\)

Concentration of \(HCl =0.5 M\).

No. of milli moles of \(HCl =10\)

No. of milli moles of \(Ca ( OH )_2=5\).

\(\text { i.e. }M _{ Ca ( OH )_2}=\frac{\text { no. of milli moles }}{ V ( ml )}=\frac{5}{10}\)

\(=0.5\,M.\)

Reaction with \(H _2 SO _4\)

\(Ca ( OH )_2+ H _2 SO _4 \rightarrow CaSO _4+2 H _2 O\)

No. of milli moles of \(Ca ( OH )_2=20 \times 0.5\)

\(=10\)

i.e. no. of milli moles of \(H _2 SO _4=10\)

\(\Rightarrow M _{ H _2 so }=\frac{\text { no. of mil lim oles }}{ V ( ml )}\)

\(=\frac{10}{10}\)

\(=1\,M\)