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An impure hydrocarbon fuel is burned in the apparatus in Figure 5 - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2020 - Paper 1
Question 6
An impure hydrocarbon fuel is burned in the apparatus in Figure 5. When the fuel is burned: - the funnel becomes hot - a colourless liquid forms in tube A - the ind... show full transcript
Worked Solution & Example Answer:An impure hydrocarbon fuel is burned in the apparatus in Figure 5 - Edexcel - GCSE Chemistry Combined Science - Question 6 - 2020 - Paper 1
Step 1
Step 2
a colourless liquid forms in tube A
Answer
During combustion, water vapor is produced as a byproduct. As the gases pass through tube A, they cool down, leading to condensation of water vapor into a colourless liquid. The presence of water indicates that the combustion of hydrocarbons primarily generates water and carbon dioxide, along with other possible products depending on the impurities in the fuel.
Step 3
the indicator in tube B changes colour to show an acidic gas
Answer
The combustion of hydrocarbons also produces carbon dioxide (CO₂) as a byproduct. When CO₂ dissolves in water, it forms carbonic acid (H₂CO₃), which can lower the pH of the indicator solution in tube B. This change in acidity causes the indicator to change color, signaling the presence of an acidic gas resulting from the combustion process.