How many moles of MgCl2 are there in 338 g of the compound

atomic mass of magnesium = 24.305

atomic mass of chlorine = 35.453

molecular mass of MgCl2 = 24.305+2*35.453 = 95.211

Number of moles in 338 g of pure MgCl2

= 338/95.211 = 3.55001 moles

Ans. there are 3.55 moles of MgCl2 in 338 g of the substance.