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Propene is an alkene - Edexcel - GCSE Chemistry - Question 6 - 2012 - Paper 1
Question 6
Propene is an alkene. The formula of its molecule is C₃H₆. (a) (i) Draw the structure of a propene molecule, showing all of the bonds. (ii) One molecule of decane... show full transcript
Worked Solution & Example Answer:Propene is an alkene - Edexcel - GCSE Chemistry - Question 6 - 2012 - Paper 1
Step 1
Draw the structure of a propene molecule, showing all of the bonds.
Answer
The structure of propene (C₃H₆) features a double bond between two carbon atoms.
Here is a simple representation:
H H
\ /
C
/ \
H C = C
/ \
H H
This diagram illustrates all the bonds in the propene molecule, including the double bond between the central carbon atoms.
Step 2
One molecule of decane, C₁₀H₂₂, can be cracked to produce one molecule of propene and one molecule of an alkane X only. Complete the sentence by putting a cross (✗) in the box next to your answer.
Answer
To identify which alkane X is produced when decane is cracked, we need to consider the molecular structure. Since one molecule of propene (C₃H₆) is produced, the remaining alkane must have the formula:
C₁₀H₂₂ - C₃H₆ = C₇H₁₆.
Therefore, the correct formula of alkane X is C₇H₁₆.
This corresponds to option B C₈H₁₆.
Step 3
Given a sample of each gas, describe a test to show which gas is propane and which gas is propene.
Answer
To differentiate between propane and propene, perform the following tests:
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Bromine Water Test: Add a few drops of bromine water to each gas sample in separate test tubes. Propene will decolorize bromine water due to its ability to undergo addition reactions (due to the double bond), while propane will not.
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Flame Test: Burn a small amount of each gas. Propane will produce a clean flame, whereas propene may produce a sootier flame due to its higher carbon content.
These tests help identify which gas is propane and which is propene.