Question

A chemistry student weighs out 0.117 g of citric acid (H.CHO), a triprotic acid, into a 250 mL volumetric flask and dilutes to the mark with distilled water. He plans to titrate the acid with 0.0800 M 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

Balanced chemical equation is:

H3C6H5O7 + 3 NaOH ---> Na3C6H5O7 + 3 H2O

Molar mass of H3C6H5O7,

MM = 8*MM(H) + 6*MM(C) + 7*MM(O)

= 8*1.008 + 6*12.01 + 7*16.0

= 192.124 g/mol

mass(H3C6H5O7)= 0.117 g

use:

number of mol of H3C6H5O7,

n = mass of H3C6H5O7/molar mass of H3C6H5O7

=(0.117 g)/(1.921*10^2 g/mol)

= 6.09*10^-4 mol

According to balanced equation

mol of NaOH reacted = (3/1)* moles of H3C6H5O7

= (3/1)*6.09*10^-4

= 1.827*10^-3 mol

This is number of moles of NaOH

use:

M = number of mol / volume in L

0.08 = 1.827*10^-3/ volume in L

volume = 0.0228 L

volume = 22.8 mL

Answer: 22.8 mL