At elevated temperatures, copper (Cu) reacts with sulfur (S) to form cuprous sul

Question

At elevated temperatures, copper (Cu) reacts with sulfur (S) to form cuprous sulfide, Cu_2S. When a quantity of 100.0 g of copper is heated with 50.0 g of sulfur, the amount of cuprous sulfide formed is: 62.61 g 125.23 g 159.15 g 248.21 g 496.42 g None of the above; the correct amount is___g At elevated temperatures, aluminum (Al) reacts with manganous oxide (MnO) to form aluminum Oxide (Al_2O_3) and manganese (Mn). A quantity of 110.0 g of Al is heated with 200.0 g of MnO. The amount of Mn recovered at the end of the reaction is found to be 105.3 g. The percent yield of Mn is: 22.7% 31.3% 47.0% 52.1% 68.0% None of the above; the correct yield is___g

Explanation / Answer

6.

2 Cu + S --> Cu2S

Moles of Cu = 100/ 63.5 = 1.57

Moles of S = 50 / 32 = 1.56

Cu is the limiting reagent.

Moles of Cu2S formed = 1.57 / 2 = 0.79

Mass of  Cu2S formed = 0.79 * 159.16 = 125.23 g

Option b.

7.

2 Al + 3 MnO --> Al2O3 + 3 Mn

Moles of Al = 110 / 26.98 = 4.08

Moles of MnO = 200 / 70.94 = 2.82

MnO is the limiting reagent.

Moles of Mn formed = 2.82 * 3 / 3 = 2.82

Theoretical mass of Mn formed = 2.82 * 54.94 = 154.89 g

Actual mass of Mn formed = 105.3 g

% yield = 105.3 / 154.89 = 68 %

Option e.

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