Question

What mass of KOH is required to neutralize 200mL of 3.16 M HNO3?

Answer 1

find the mole for HNO3 using n = MV where M is the molarity and V is the volume in Liters.

then use the balance equation;

KOH + HNO3 --> KNO3 + H2O

the reaction is 1:1 so the mole you calculated for HNO3 is also the mole for KOH.
i.e. mole KOH = mole HNO3.

then convert the mole to mass using the molar mass of KOH (obtain from periodic table) to get the mass for KOH.

hope that helps...