Molarity of Ba(OH)2 solution = 20171×2=40171 M
So, the reaction involved in titration is:
Ba(OH)2+H2SO4→BaSO4+2H2O
Thus 1 mol of the base (Ba(OH)2) reacts with with one mole of the acid (H2SO4)
Hence we can write, M1V1=M2V2
Where, M1 = molarity of Ba(OH)2
V1 = volume of Ba(OH)2
M2 = molarity of H2SO4
V2 = volume of H2SO4
∴40171×25=M2×35
⇒M2=40×25171×35=0.167M