chem question help

Question

A volume of 11.0 mL of a 0.32 M solution of hydrogen phosphate (or phosphoric acid) reacts completely with 71.0 milliliters of sodium hydroxide. What is the molarity of the sodium hydroxide solution?

Answer 1

The answer is 0.15 M

First the find the moles of Phosphoric acid = Molarity X Volume in liters = 0.32 X 0.011 liters = 0.00352 moles of Phoshporic acid.

Phosphoric acid and Sodium hydroxide react with each in other 1:3 ratio. Therefore moles of Sodium hydroxide are 0.00352 X 3 = 0.01056

Molarity of sodium hydroxide = moles/liters

0.01056/0.071 liters = 0.15