the balanced equation for the reaction is as follows;
4HCl + O₂ ---> 2Cl₂ + 2H₂O
stoichiometry of HCl to Cl₂ is 4:2
Avagadros law states that volume is proportional to number of moles of gas when pressure and temperature are constant
therefore volume ratio is equal to the molar ratio
therefore molar ratio of HCl to Cl₂ is 4:2
volume of HCl reacted - 0.98 L
therefore volume of Cl₂ formed - 0.98 L / 2 = 0.49 L
