The correct one would be volume
Gases take the shape of their container and have no definite volume because they can diffuse indefinitely. Answer C.
3.52g BiCl3 × 1 mol BiCl3/ 315.34g BiCl3 × 3 mol Cl/ 2 mol BiCl3 × 70.906g Cl/ 1 mol Cl= 1.187 g Cl
% by mass = (mass solute/mass solution)*100%
mass of the solute = 54.7 g
mass of the solution = mass solute + mass solvent=54.7+500=554.7 g
% by mass = (54.7/554.7)*100%≈0.0986*100% = 9.86%