Explaining what's happening
2 marks · EasyA reaction in a beaker starts with 50 reacting particles per cm³. After a few minutes, only 10 reacting particles per cm³ remain.
Calculate the percentage decrease in the number of reacting particles per cm³ during the reaction.
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80\% (±0)
Also accept: 80 percent
Common mistakes: Only subtracting, not calculating as a percentage; Wrong base for percentage calculation
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Marking points
M1 · 1 mark · Subtracts final from initial number of reacting particles and uses the correct base (initial value) for calculation.
A1 · 1 mark · Correct final percentage decrease: 80%. (follow-through)
Worked solution
Initial particles per cm³ = 50
Final particles per cm³ = 10