A sample containing aluminum weighing 10.0g yielded 2.0g of aluminum sulphide. What is the percentage of aluminum (atomic mass 27.0) in the sample? Sulphur (atomic mass 32.0) =
Correct answer: A. 2.0 X27/150 x100
- A. 2.0 X27/150 x100
- B. 2.0/10 X 2 X 27/150 X 100
- C. 2.0/10 X 27/1500 X 100
- D. 2.0/10 X 150/3 X 27 X 100
Explanation
Mass of aluminum in formula: 2×27=54 gMolar mass of Al₂S₃: 2×27+3×32=54+96=150 g54/150x100=36%
This question appeared on the ETEA MDCAT 2011 paper, which you can sit online with every answer explained.
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About Theoretical and Percentage Yield
Theoretical yield is the maximum product predicted from a balanced equation and the amount of limiting reactant. Work includes identifying the limiting reagent, comparing theoretical and actual yield, and calculating percentage yield using stoichiometric mole relationships.
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