Question

If 4.88 grams of zn react with 5.03 grams of s8 to produce 6.02 grams of zns, what are the theoretical yield and percent yield of this reaction? be sure to show the work that you did to solve this problem. unbalanced equation: zn + s8 zns

Answer 1

Balance the equation
    8Zn + S8 -----> 8ZnS
    work out how much ZnS is possible if all of each reagent were to react. The reagent that produces the least product is the limiting reagent.
    moles Zn = mass / molar mass = 4.88 g / 65.38 g/mol = 0.07464 moles
  8 moles Zn reacts to form 8 moles ZnS
  Therefore moles ZnS possible = moles Zn = 0.07464 moles

    moles S8 = 5.03 g / 256.48 g/mol = 0.01961 mol
  1 mole S8 reacts to form 8 moles ZnS
  Therefore moles ZnS possible = 8 x moles S8 = 0.1569 mol

    The amount of Zn provided gives the least ZnS, therefore Zn is the limiting reagent.
    The theoretical yield is the maximum possible yield possible from the reagents provided. It is the amount of product that will form if all the limiting reagent reacts.
  So in this case 4.88 g Zn yields 0.07464 mol ZnS

    theoretical mass ZnS = molar mass x moles
  = 97.44 g/mol x 0.07464 mol
  = 7.27 g

    % yield = actual yield / theoretical yield x 100/1
  = 6.02 g / 7.27 g x 100/1
  = 82.8 %