ONE-EIGHTH STAGE 2025
Opoku Ware School: 67 points
Amenfiman SHS: 36 points
Fijai SHS: 30 points
ROUND 4 - TRUE OR FALSE
PREAMBLE
1. Aromatic hydrocarbons form the largest fraction of crude petroleum.
ANSWER: FALSE
2. Fractional distillation of crude oil separates components based on differences in boiling points.
ANSWER: TRUE
3. Natural gas is mainly composed of methane with smaller amounts of other light hydrocarbons.
ANSWER: TRUE
EXPLANATION:
Crude petroleum is overwhelmingly alkanes by mass, not aromatics.
Fractional distillation exploits differing boiling points to separate hydrocarbon fractions.
Natural gas is predominantly methane, with smaller amounts of ethane, propane and butane.
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PRACTICE QUESTIONS
PREAMBLE 1
Consider fossil fuels.
1. Coal, crude oil and natural gas are fossil fuels.
ANSWER: TRUE
EXPLANATION:
They formed from the remains of ancient organisms.
2. Fossil fuels are renewable resources.
ANSWER: FALSE
EXPLANATION:
They take millions of years to form, so they are non-renewable.
3. Burning fossil fuels releases carbon dioxide.
ANSWER: TRUE
EXPLANATION:
Their carbon is oxidised to $CO_2$.
PREAMBLE 2
Consider the combustion of hydrocarbon fuels.
1. Complete combustion of methane gives carbon dioxide and water.
ANSWER: TRUE
EXPLANATION:
$CH_4+2O_2\rightarrow CO_2+2H_2O$
2. Incomplete combustion of a fuel can produce carbon monoxide.
ANSWER: TRUE
EXPLANATION:
With too little oxygen, carbon is only partly oxidised.
3. Carbon monoxide is harmless because it has no smell.
ANSWER: FALSE
EXPLANATION:
It is very poisonous: it binds to haemoglobin and stops oxygen transport.