The correct option is
D 4.0MThe acid solution is titration to neutralized.
Hence, at the equivalence point,
Moles of OH− ions = Moles of H+ ions. (1)
1 mole of Ba(OH)2 gives 2 moles of OH−
∴ Moles of OH−=2× Moles of Ba(OH)2
Moles of OH−=2×[Molarity×VolumeofBa(OH)2]
Moles of OH−=0.05(2)
Moles of H+ ion =Moles of HNO3
Moles of H+ ion =Concentration×Volume of HNO3
Moles of H+ ion =Concentration×12.5×10−3
From (1) and (2),
0.05= (Concentration of acid) ×12.5×10−3
∴ Concentration of acid =4.0 M