How many milliliters of a 2.5 M LiOH solution are needed to completely neutralize 25 mL of a 1.0 M H2SO4 solution?

20 ml.

Explanation:

molarity of LioH (M1) = 2.5M

Volume of LioH (V1) = ?

Normality of LiOH (N1) = M1*valence factor=2.5*1=2.5 N

Volume of acid H2SO4 (V2) = 25 ml

molarity of acid H2SO4 (M2) = 1.0 M

Normality of acid H2SO4 (N2) = M2*valance factor=1.0*2=2.0

now, according to normality equation,

V1. N1=V2. N2

or, V1*2.5=25*2

or, V1=50/2.5

or, V1=20 ml

Therefore, V1=20 ml.