how many molecules of chlorine gas must be reated with excess sodium iodide if 32.2*10^22 formula units of sodium chloride are needed?
2NaI + Cl2 --> 2NaCl + I2
32.2*10^22 / 6.02*10^23 = 0.53 moles NaCl
One mole of Cl2 produces 2 moles of NaCl, so half that will be the amount of Cl2 needed.