Question

The concentration of HCl can be determined by titration with a primary standard such as Na2CO3 (sodium carbonate). The titration reaction is
CO3^(2-) + 2H+ yields H2O + CO2
What is the concentration of HCl if 25.9 mL of HCl was needed to to react with 0.311 g of Na2CO3 to reach the end point?

Answer 1

$\mathrm{Na}_{2} \mathrm{CO} 3+2 \mathrm{HCl}=2 \mathrm{NaCl}+\mathrm{H} 2 \mathrm{O}+\mathrm{CO} 2$

Moles of $\mathrm{Na} 2 \mathrm{CO} 3=$ mass $/$ molar mass of $\mathrm{Na} 2 \mathrm{CO} 3$

$=0.311 / 105.99=0.002934 \mathrm{~mol}$

Moles of $\mathrm{HCl}=2 \times$ moles of $\mathrm{Na} 2 \mathrm{CO} 3$

$=2 \times 0.002934=0.005868 \mathrm{~mol}$

Concentration of $\mathrm{HCl}=$ moles $/$ volume of $\mathrm{HCl}$

$=0.005868 / 0.0259$

$=0.227 \mathrm{M}$