The correct option is C 10.96
The reaction proceeds as :
NaOH+HCl⇌NaCl+H2O
As we know,
1 mole of HCl reacts with the 1 mole of NaOH.
Lets find the moles of solution,
Moles of HCl in 9.9 ml of 1 M solution = 9.91000×1=0.0099 mol HCl
Moles of NaOH in 100 ml of 0.1 M solution =1001000×0.1=0.01 mol NaOH
On mixing the 0.0099 mole of HCl will be neutralised = 0.01 - 0.0099 =1×10−4 mol NaOH dissolved in 109.9 mL solution.
Hence, the molarity of NaOH solution=[OH]−=1×10−4 mol109.91000L=9.099×10−4 MpOH=−log[OH]−=−log(9.099×10−4)pOH=−(0.96−4)=3.04pH+pOH=14pH=14−3.04=10.96