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Chemistry µGCSE:

Percentage Yield

10 quick questions - for GCSE and iGCSE

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10 minutes maximum! (can you do it in 5?)

Grab a calculator and Periodic Table - time for some maths!

 

 
1. The equation to calculate percentage yield is ….
  • A.   percentage yield = (actual mass of product/maximum theoretical mass of product) x 100
  • B.   percentage yield = (maximum theoretical mass of product/actual mass of product) x 100
  • C.   percentage yield = (actual mass of product/mass of reactant used) x 100
  • D.   percentage yield = (mass of reactant used/actual mass of product) x 100

2. Tungsten metal was produced by reducing tungsten fluoride with hydrogen. A student calculated that a mass of 52.0g of tungsten should be formed. He actually obtained 43.2g of tungsten.
What is the percentage yield of tungsten in this experiment?

  • A. 16.9%
  • B. 83.0%
  • C. 83.1%
  • D. 120%

Q3+4: A student synthesized 12.3g of aspirin from 13.8g of salicylic acid. He calculated that the maximum possible mass of aspirin which he could obtain was 18.0g.

3. a possible reason for the student obtaining less aspirin than expected is …

  • A.   the reaction may not have gone to completion
  • B.   some aspirin may have been lost during separation from the reaction mixture
  • C.   some of the salicylic acid may have reacted to produce another product
  • D.   all of the above

4. The percentage yield of aspirin in this experiment was ……..

  • A. 112%
  • B. 89.1%
  • C. 76.7%
  • D. 68.3%


Q5+6. 

21.7g of mercury(II)oxide was decomposed by heating and 9.0g of mercury was collected.

The equation for the reaction is:

2HgO (s)      2Hg (l)   +  O2 (g)

 

5. The mass of 1 mole of mercury(II)oxide and the number of moles in 21.7g is ….

  Mass of 1 mole of mercury(II)oxide  /g Number of moles in 21.7g
A 217 0.1
B 217 0.05
   C 88 0.25
D 88 0.12

6. The maximum mass of mercury which could be obtained in this experiment and the % yield are ….

  Maximum possible mass of mercury  /g % yield
A 10.1 89.1
B 10.1 112.2
   C 20.1 44.8
D 20.1 223.3

 

 Q7+8.

50g of calcium carbonate was strongly heated resulting in thermal decomposition.
The equation for the reaction is:

CaCO3 (s  CaO (s) +   CO2 (g)

 

Calcium Carbonate Rocks

Ferdous
CC-BY-SA 3.0


7. What is the molar mass of calcium carbonate and how many moles of CaCO3 are in 50 g?

  Molar mass of CaCO3 /g Number of moles of CaCO3 in 50g
A 68 1.36
B 68 0.74
   C 100 2
D 100 0.5
8. What mass of calcium oxide is obtained from the thermal decomposition of 50 g of calcium carbonate if the reaction has a 40% yield?
  • A.   11.2g
  • B.   16.6g
  • C.   16.8g
  • D.   28.0g

 

Q9+10.
A manufacturer produced 51kg of ammonia by reacting 56kg of nitrogen with excess hydrogen in the Haber process.
The equation for this reaction is:

N2 + 3H2 ⇌ 2NH3

Ammonia 3D balls

9. The maximum possible yield of ammonia, if the reaction went to completion, is …….

  • A. 34kg
  • B. 56kg
  • C. 68kg
  • D. 136kg

10. The percentage yield of ammonia in this reaction is …..

  • A. 38%
  • B. 75%
  • C. 82%
  • D. 91%