162 grams First, look up the atomic weight of all involved elements Atomic weight Magnesium = 24.305 Atomic weight Chlorine = 35.453 Now, calculate the molar mass of MgCl2 24.305 + 2 * 35.453 = 95.211 g/mol Finally, multiply the molar mass by the number of moles 95.211 g/mol * 1.70 mol = 161.8587 g Rounding to 3 significant figures gives 162 grams.