Question

The concentration of HCl can be determined by titration with a primary standard such as sodium carbonate (Na2CO3). The titration reaction is CO3 2 H H2OCO2 What is the concentration of HCl if 35.5 mL of HCl was needed to to react with 0.201 g of Na2CO3 to reach the end point? concentration:

Answer 1

Molar mass of Na2CO3,
MM = 2*MM(Na) + 1*MM(C) + 3*MM(O)
= 2*22.99 + 1*12.01 + 3*16.0
= 105.99 g/mol


mass(Na2CO3)= 0.201 g

use:
number of mol of Na2CO3,
n = mass of Na2CO3/molar mass of Na2CO3
=(0.201 g)/(1.06*10^2 g/mol)
= 1.896*10^-3 mol
According to balanced equation
mol of H+ reacted = (2/1)* moles of Na2CO3
= (2/1)*1.896*10^-3
= 3.793*10^-3 mol
This is number of moles of H+
volume , V = 35.5 mL
= 3.55*10^-2 L


use:
Molarity,
M = number of mol / volume in L
= 3.793*10^-3/3.55*10^-2
= 0.1068 M
Answer: 0.107 M