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.
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Answer
The structure of a propene molecule can be represented as:
H H
\ /
C=C
/ \
H H
This diagram shows the double bond between the two carbon atoms (C=C) and the single bonds to the hydrogen atoms.
Step 2
The formula of a molecule of alkane X is
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Answer
The correct option is:
A C₈H₁₄
This is because cracking one molecule of decane will yield propene (C₃H₆) and one alkane, which must be octane (C₈H₁₄) to balance the equation.
Step 3
Describe a test to show which gas is propane and which gas is propene.
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Answer
To distinguish between propane and propene:
Test for Unsaturation:
Propene is an alkene and has a double bond, which means it is unsaturated.
You can use bromine water for this test. Propene will decolorize the bromine water, turning it from brown to colorless, indicating the presence of the double bond.
In contrast, propane, being a saturated alkane, will not change the color of the bromine water.
Test with a Flame:
Both gases can be tested using a lighter. When burned, propane produces a clean flame, while propene produces a sooty flame because of incomplete combustion due to higher reactivity.
