The origin of crude oil
2 marks · EasyCrude oil is a mixture containing many different hydrocarbons. A crude oil sample has molecules with an average of 10 carbon atoms for every hydrocarbon molecule. If another sample has 50 such molecules, calculate the total number of carbon atoms in this sample.
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500 (±0)
(a) 500 · must show Calculation: 10 × 50, Correct final answer
Also accept: number with calculation shown: 10 × 50 = 500
Common mistakes: Adding rather than multiplying; Forgetting to multiply by the number of molecules
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Marking points
M1 (a) · 1 mark · Multiplies the average number of carbon atoms (10) by the number of molecules (50).
A1 (a) · 1 mark · Gives the correct answer: 500. (follow-through)
Worked solution
Each molecule contains 10 carbon atoms. There are 50 molecules.
So, there are 500 carbon atoms in total.