58.5g of sodium iodide are dissolved in 0.5dm3. what concentration would this be?

percent by mass=(mass of solute/ mass of solution)*100 %

mass of solute=58.5 g

density (H₂O)=1 g/cm³*(1000 cm³/1dm³)=1000 g/dm³

mass of solvent (H₂O)=0.5 dm³ * (1000 g/dm³)=500 g
mass of solution=mass of solvent + mass of solut
mass of solution=58.5 g+500 g=558.5 g

% mass=(58.5 g/558.5 g) * 100%=10.47% of Na.

solution:  10.47% of Na.