Question

A chemistry student weighs out 0.172g of sulfurous acid H2SO3, a diprotic acid, into a 250.mL volumetric flask and dilutes to the mark with distilled water. He plans to titrate the acid with 0.0800M NaOH solution.

Calculate the volume of NaOH solution the student will need to add to reach the final equivalence point. Round your answer to 3 significant digits.

Answer 1

The balanced chemical equation for the reaction between H2SO3 and NaOH is:

H2SO3 + 2 NaOH → Na2SO3 + 2 H2O

From the equation, we see that 1 mole of H2SO3 reacts with 2 moles of NaOH.

First, we need to calculate the number of moles of H2SO3 in the volumetric flask:

moles of H2SO3 = mass / molar mass

moles of H2SO3 = 0.172 g / 82.07 g/mol

moles of H2SO3 = 0.002096 mol

Since H2SO3 is a diprotic acid, it can react with two moles of NaOH. Therefore, the number of moles of NaOH required to reach the equivalence point is:

moles of NaOH = 2 * moles of H2SO3

moles of NaOH = 2 * 0.002096 mol

moles of NaOH = 0.004192 mol

Finally, we can calculate the volume of NaOH solution required using the formula:

volume of NaOH solution = moles of NaOH / molarity of NaOH

volume of NaOH solution = 0.004192 mol / 0.0800 mol/L

volume of NaOH solution = 0.0524 L

Therefore, the volume of NaOH solution the student will need to add to reach the final equivalence point is 0.0524 L (rounded to 3 significant digits).