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4. (a) Propene is a gaseous hydrocarbon - Edexcel - GCSE Chemistry - Question 4 - 2015 - Paper 1
Question 4
4. (a) Propene is a gaseous hydrocarbon. Draw the structure of a molecule of propene, showing all bonds. (b) Nitrogen reacts with hydrogen to form ammonia. N₂(g) ... show full transcript
Worked Solution & Example Answer:4. (a) Propene is a gaseous hydrocarbon - Edexcel - GCSE Chemistry - Question 4 - 2015 - Paper 1
Step 1
Draw the structure of a molecule of propene, showing all bonds.
Answer
The structure of propene (C₃H₆) includes three carbon atoms with one double bond between two of them. Each carbon atom is bonded to sufficient hydrogen atoms to complete their tetravalence. The correct structure can be represented as:
H H
\ /
C = C
/ \
H C
|
H
This diagram shows all the bonds in the propene molecule.
Step 2
Calculate the minimum volume of nitrogen, in dm³, required to react completely with 1000 dm³ of hydrogen.
Answer
To balance the reaction:
N₂(g) + 3H₂(g) ⇌ 2NH₃(g)
From the balanced equation, 1 volume of nitrogen reacts with 3 volumes of hydrogen. Therefore, to determine the volume of nitrogen required to react with 1000 dm³ of hydrogen:
a. Use the ratio:
-
If 3 dm³ of H₂ uses 1 dm³ of N₂, then 1000 dm³ of H₂ will use:
Thus, we choose A 333 dm³.
Step 3
Explain which gas or gases will be present when equilibrium is reached.
Answer
At equilibrium, when the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g) has reached a state of balance, all species will still be present.
This includes:
- Nitrogen (N₂)
- Hydrogen (H₂)
- Ammonia (NH₃)
However, the concentrations of these gases will no longer change, implying that at equilibrium, the forward and reverse reactions occur at equal rates.
Step 4
Explain the effect on the equilibrium yield of ammonia, if the process is carried out at a pressure higher than 200 atm.
Answer
Increasing the pressure in the Haber process shifts the position of equilibrium towards the side with the fewer moles of gas. In this case, there are:
- 4 moles of gas (1 mole of N₂ and 3 moles of H₂) on the reactant side.
- 2 moles of gas (2 moles of NH₃) on the product side.
Thus, higher pressure favors the formation of ammonia. Therefore, as pressure increases beyond 200 atm, the yield of ammonia will increase.
Step 5
Explain the effect on the rate of attainment of equilibrium, if the process is carried out at a pressure higher than 200 atm.
Answer
Increasing the pressure increases the concentration of the gaseous reactants, leading to more frequent collisions between nitrogen and hydrogen molecules. This results in:
- An increased rate of reaction.
- Faster attainment of equilibrium due to a higher collision rate and more interactions between molecules, effectively speeding up the process.