S reacts with F2 in a synthesis react what mass in g of SF6 is produced by the reaction of 3.5 g of S with 4.5 g of Fl ? How many g of the excess reactant remain?

Question

Do your results agree with the law of conservation of mass?

Answer 1

As with the previous questions, start with a balanced equation:

S + 3F₂ ==> SF₆

Find moles of each reactant:

moles S = 3.5 g S x 1 mol/32 g = 0.109 moles S

moles F₂ = 4.5 g x 1 mol/38 g = 0.118 moles F₂ (this is limiting since you need 3 moles F₂ for each 1 mole of S, and thus there isn't enough F₂)

Find theoretical yield of SF₆:

0.118 moles F₂ x 1 mole SF₆/3 moles F₂ x 146 g/mole SF₆ = 5.7 g SF₆

Excess reactant is S, and the mass remaining is...

0.118 moles F₂ x 1 mole S/3 moles F₂ = 0.0393 moles S used up.

mass remaining = 0.109 moles - 0.0393 moles = 0.0697 moles S x 32 g/mole = 2.2 g S left over.