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9 (a) An impure hydrocarbon fuel is burned in the apparatus in Figure 7 - Edexcel - GCSE Chemistry - Question 9 - 2020 - Paper 1
Question 9
9 (a) An impure hydrocarbon fuel is burned in the apparatus in Figure 7. When the fuel is burned: - the funnel becomes hot - a colourless liquid forms in tube A - t... show full transcript
Worked Solution & Example Answer:9 (a) An impure hydrocarbon fuel is burned in the apparatus in Figure 7 - Edexcel - GCSE Chemistry - Question 9 - 2020 - Paper 1
Step 1
Step 2
A colourless liquid forms in tube A
Answer
The formation of a colourless liquid in tube A indicates that condensation is occurring. This liquid is likely water vapor that has condensed as a product of combustion and can also consist of unreacted hydrocarbons. The combustion of hydrocarbons produces water (H₂O) and carbon dioxide (CO₂), and as gas cools, it condenses into a liquid.
Step 3
The indicator in tube B changes colour to show an acidic gas
Answer
The indicator in tube B changes colour due to the presence of carbon dioxide (CO₂) which is produced during the combustion of the hydrocarbon fuel. When dissolved in water, carbon dioxide forms carbonic acid (H₂CO₃), which decreases the pH, causing the indicator to change colour, demonstrating the acidity of the gas.