Determining the number chloride molecules that will result from this reaction requires we first determine the number of moles of arsenic and the number of moles of chlorine on hand.
1.587 grams of arsenic divided by its atomic weight of 74.92 grams per mole results in 0.0212 moles.
We do the same for chlorine. 2.755 grams of chlorine divided by 35.45 grams per mole gives us 0.106 moles.
0.106 moles divided by .0212 moles equals 5; therefore, the simplest formula of the chloride produced will be AsCl₅.