Chemistry - Solution Stoichiometry

Question

A 701- mL sample of unknown HCl solution reacts completely with Na2CO3 to form 12.1g CO2. What was the concentration of the HCl solution?

Answer 1

First write the chemical reaction equation:

2HCl + Na₂CO₃ → 2NaCl + H₂O + CO₂

Next, convert 12.1 g of CO₂ into moles using the molar mass. The molar mass is 12.011 + 15.999(2) = 44.009 g/mol so (12.1 g)/(44.009 g/mol) = 0,2749 moles

The chemical reaction equation tells us that for every 1 mole of CO₂ produced, it required 2 moles of HCl so, since there were 0,2749 moles of CO₂ produced, there must have been twice that or 0.5499 moles of HCl used.

The concentration is so many moles per liter of solvent therefore it would be (0.5499 moles)/(0.701 liters) = 0.784 M solution of HCl