determining the volume of base needed to titrate

Question

A chemistry student weighs out 0.206 g of hypobromous acid HBrO into a 250.mL volumetric flask and dilutes to the mark with distilled water. He plans to titrate the acid with 0.1200 M NaOH solution. Calculate the volume of  NaOH solution the student will need to add to reach the equivalence point. Round your answer to 3 significant digits.

Answer 1

This problem is an acid/base titration with a weak acid and strong base. It asks for the amount of NaOH needed reach the equivalence point, or the measured volume where all of the HBrO has been neutralized.

First, we need to convert grams of HBrO into moles by dividing the amount by the molar mass of the acid as follows: .206g/ 96.91g/mol= 2.13x10^-3 moles HBrO

Next, let's write out the neutralization reaction for this titration

HBrO + NaOH→ BrO^- +H₂O

Since HBrO is a monoprotic acid and NaOH is a monoprotic base, at the equivalence point, the moles of NaOH needed to neutralize the acid is equal to the moles of HBrO present. Thus, 2.13x10^-3 moles of NaOH is needed to neutralize the acid. Now, we need to convert the moles of NaOH into volume using the known molarity of .1200M NaOH.

The formula M=mols/L can be rearranged into L=mols/M, and we can plug in the numbers.

L=2.13x10^-3mols/.1200M= .0177L or 17.7ml with three significant figures.