A student reacts 28 grams of iron with 24 grams of sulfur to produce iron(II) su

Question

A student reacts 28 grams of iron with 24 grams of sulfur to produce iron(II) sulfide (FeS), but has some unreacted chemicals left over at the end of the reaction. How much of which chemicals are left over and why? A. Iron is left over because there are fewer moles of it present initially. There are 8 grams of it left. Sulfur is left over because there are more moles of it present initially. There are 8 grams of it left. B. C. Sulfur is left over because there is less mass of it present initially. There are 8 grams of it left. Both chemicals are left over because neither is the limiting reagent. There are 8 grams of each left. D.

Explanation / Answer

Fe + S - - - - - - > FeS

First find the limiting reagent:

Number of moles of Fe = weight / molar mass

= 28 g / 55.845 g mol-1

= 0.501 moles

Similarly, Number of moles of S = 24 g / 32 gmol-1

= 0.75 moles

So, Fe is the limiting reagent.

excess reagent ie S left =( 0.75 - 0.501) moles of S

= 0.249 moles of S

So, weight of S left = 0.249 mol * molar mass of S

= 0.249 mol * 32 g / mol

= 8 grams

So, option B is the correct choice.

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