Propenes can be produced by the cracking of some hydrocarbons obtained from crude oil - Edexcel - GCSE Chemistry - Question 5 - 2019 - Paper 1
Question 5
Propenes can be produced by the cracking of some hydrocarbons obtained from crude oil. The equation shows the cracking of one molecule of decane to produce one molec... show full transcript
Worked Solution & Example Answer:Propenes can be produced by the cracking of some hydrocarbons obtained from crude oil - Edexcel - GCSE Chemistry - Question 5 - 2019 - Paper 1
Step 1
Calculate the values of x and y in $C_yH_x$
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Answer
From the equation of cracking decane, we start with:
C10H22→C4H10+CyHx
To balance the carbon atoms, we have 4 from butene and y from the other product, hence:
10=4+y⇒y=6
For the hydrogen atoms:
22=10+x⇒x=12
Thus, the values are:
x=12
y=6.
Step 2
State the total mass of products formed if 25 g of decane is cracked in this way
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Answer
To find the total mass of products formed, we can use the mass conservation principle. The mass of the products will equal the mass of the reactants.
Therefore, if 25 g of decane is cracked, the total mass of products formed will also be:
Total mass of products=25extg
Step 3
Complete Figure 9 to show the electrons of the C=C double bond.
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Answer
In Figure 9, there should be a representation of the double bond between the two carbon atoms.
To show the electrons, place:
4 electrons shown between the two carbon atoms: typically represented as dots or crosses.
Step 4
Give the name of another product of the incomplete combustion of ethene.
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Answer
The incomplete combustion of ethene typically produces carbon monoxide (CO) as another product in addition to water (H₂O).
Step 5
Explain how the structure of substance X shows that it is an unsaturated hydrocarbon.
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Answer
Substance X contains at least one C=C (double bond) or C≡C (triple bond). The presence of double or triple bonds indicates that it is unsaturated since saturated hydrocarbons only contain single bonds between carbon atoms.
Step 6
Explain the results of the bromine water test.
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Answer
The results indicate:
Hydrocarbon A, being an alkane, does not react with bromine water, as shown by the mixture turning colourless.
Hydrocarbon B, being an alkene, reacts with bromine water, decolourizing it from orange to colourless due to the addition reaction, showing the unsaturation in the hydrocarbon.
