25 ~mL, 0.2 MCa(OH)_2 is neutralised by 10 ~mL of 1 MHCl . Then pH...

Number of millimoles of base (i.e., \left.\mathrm{Ca}(\mathrm{OH})_2\right)=N_1 V_1=2 \times M_1 \times V_1=2 \times 0.2 \times 25=10$Number of millimoles of acid (i.e.,$\mathrm{HCl})=\mathrm{N}_2 V_2$=10$\times$1=10 As, no. of millimoles of acid = no. of millimoles of base$\therefore$Acid is completely neutralised by base forming a neutral solution.$\therefore \mathrm{pH}$of the resulting solution$=7.