Answer to Question #184497 in General Chemistry for Shapaka Nikodemus

Question

 If 15.65 mL of aq. HCl is required to neutralise 20.00 mL of the sodium carbonate 

solution from question 4 above, what is the molarity of the aq. HCl? (Show all steps in 

your calculation as set out below.)

(a). Write the reaction equation for the titration.

(b). Calculate the number of moles of Na2CO3 (standard solution) used in the titration.

(c). Using the balanced reaction equation, find the number of moles of HCl that 

reacted.

(d). Calculate the molarity of the HCl solution.

Answer 1

The reaction involved in this titration is

(a) $Na_2CO_3 (aq) + 2HCl \longrightarrow2NaCl+ H_2O+CO_2$

(b) mass of Na₂CO₃ = 2.5 g,molar mass of Na₂CO₃ =106

moles of Na₂CO₃ =$\frac{2.5}{106}=0.0235$

(c) from above reaction we can say that

1 mole Na₂CO₃ reacts with 2 mole HCl

so, 0.0235 mole HCl react with 0.047 mole HCl

(d) Molarity = $\frac{mole\times 1000}{volume (inmL)}$

Molarity=$\frac{0.047\times 1000}{20(inmL)}$ =2.35 M