Question

How many moles of carbon dioxide are produced when 0.2 mol of sodium carbonate reacts with excess hydrochloric acid?

Answer 1

译文
Yes, I totally agree that the answer should be 0.2mol.
Besides，if it's not excess hydrochloric acid，the answer will be 0.2 mol，too.

Answer 2

Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O

1 mol Na₂CO₃ - 1 mol CO₂

0.2 mol Na₂CO₃ - x mol CO₂

x=0.2*1/1=0.2 mol