first, write down the mass, Mr and calculate the moles of NaCl.mass = 350gMr = 24.0 + 35.5 = 58.5mol = mass/Mr = 350/58.5 = 5.98 (3s.f)now calculate the concentration in 3dm3 of watervol = 3mol = 5.98conc = moles/volume = 5.98/3 = 1.99 mol.dm3 (3 s.f)