Concept:
HCl is a strong acid and \(Ca(OH)_2\) is a strong base. If moles of \(H^+\) and \(OH^-\) are equal, the solution becomes neutral.
Step 1: Calculate moles of \(H^+\).
\[
\text{Moles of HCl}=0.01\times\frac{20}{1000}=2\times10^{-4}
\]
So,
\[
H^+=2\times10^{-4}\ \text{mol}
\]
Step 2: Calculate moles of \(OH^-\).
\[
\text{Moles of }Ca(OH)_2=0.005\times\frac{20}{1000}=1\times10^{-4}
\]
Each \(Ca(OH)_2\) gives 2 \(OH^-\):
\[
OH^-=2\times10^{-4}\ \text{mol}
\]
Step 3: Conclusion.
Moles of \(H^+\) and \(OH^-\) are equal. Hence solution is neutral:
\[
pH=7
\]