IB · IB Chemistry
IB Chemistry: Energy from fuels — Practice Questions & Answers
74 practice questions available for this topic — here are 10 with full answers and explanations.
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Practice questions with answers
1
Multiple choice · Easy
Complete combustion of a hydrocarbon produces:
- Carbon dioxide and water
- Carbon monoxide and water
- Carbon and hydrogen
- Hydrogen and oxygen
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WhyComplete combustion of a hydrocarbon in plenty of oxygen gives carbon dioxide and water only.
2
Multiple choice · Easy
Incomplete combustion of a fuel, due to a limited oxygen supply, can produce:
- Carbon monoxide and/or soot
- Only carbon dioxide
- Only water
- Oxygen gas
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WhyWith insufficient oxygen, incomplete combustion produces toxic carbon monoxide (CO) and/or carbon (soot) as well as water.
3
Multiple choice · Medium
The standard enthalpy of combustion of a fuel is always:
- Exothermic (negative)
- Endothermic (positive)
- Zero
- Always +286 kJ
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WhyCombustion releases energy, so the enthalpy of combustion is exothermic (negative).
4
Multiple choice · Medium
Which of the following is a biofuel?
- Bioethanol
- Coal
- Petrol
- Natural gas
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WhyBioethanol, produced by fermentation of plant sugars, is a biofuel. Coal, petrol and natural gas are fossil fuels.
5
Multiple choice · Medium
Which gas produced by burning fossil fuels is the main contributor to the enhanced greenhouse effect?
- Carbon dioxide
- Oxygen
- Nitrogen
- Argon
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WhyCarbon dioxide, $\text{CO}_{2}$, released by complete combustion is the major greenhouse gas from burning fossil fuels.
6
Multiple choice · Hard
What is the balanced equation for the complete combustion of propane, $\text{C}_{3}\text{H}_{8}$?
- $\text{C}_{3}\text{H}_{8} + 5\text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}$
- $\text{C}_{3}\text{H}_{8} + 3\text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}$
- $\text{C}_{3}\text{H}_{8} + \text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}$
- $\text{C}_{3}\text{H}_{8} + 4\text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}$
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Why$\text{C}_{3}\text{H}_{8} + 5\text{O}_{2} \rightarrow 3\text{CO}_{2} + 4\text{H}_{2}\text{O}$ balances 3 C, 8 H and 10 O.
7
Fill in the blank · Easy
Incomplete combustion can produce the toxic gas carbon , which binds to haemoglobin.
Answer:
monoxide / monoxide (CO)
WhyCarbon monoxide (CO) is produced when there is insufficient oxygen for complete combustion.
8
Fill in the blank · Medium
The only carbon-containing product of the complete combustion of carbon is .
Answer:
carbon dioxide / CO2 / carbon dioxide (CO2)
WhyCarbon burns completely in oxygen to form carbon dioxide: $\text{C} + \text{O}_{2} \rightarrow \text{CO}_{2}$.
9
Multiple choice · Medium
Which statement about a hydrogen-oxygen fuel cell is correct?
- Its only product is water, making it non-polluting
- It releases carbon dioxide as it operates
- It must be recharged like a normal battery
- It stops working as soon as it is switched on
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WhyThe only product of a hydrogen-oxygen fuel cell is water, so it is non-polluting.
10
Multiple choice · Medium
In a hydrogen-oxygen fuel cell, the reaction occurring at the negative electrode is
- oxidation of hydrogen
- reduction of hydrogen
- oxidation of water
- reduction of oxygen
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WhyAt the negative electrode hydrogen is oxidised, losing electrons.
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