Answer:
It depends what other values you have. Can you give more info? If they give density then you can solve for m.
Use Avogadro's number to calculate the number of moles of Mg<span>Cl2 . The number of moles of Cl is twice as </span>much, because the ratio of Cl in MgCl2 to MgCl2 is 2:1. 3.61⋅10246.022⋅10<span>23=5.99. Therefore, there are 12 moles of Cl.</span>
The first one is the answer