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When hydrogen is removed from an alkane, an alkene is formed - Edexcel - GCSE Chemistry - Question 10 - 2022 - Paper 1
Question 10
When hydrogen is removed from an alkane, an alkene is formed. This is an example of a dehydrogenation reaction. (a) Under certain conditions the dehydrogenation of ... show full transcript
Worked Solution & Example Answer:When hydrogen is removed from an alkane, an alkene is formed - Edexcel - GCSE Chemistry - Question 10 - 2022 - Paper 1
Step 1
State what is meant by dynamic in this context.
Answer
In the context of this reaction, 'dynamic' refers to the ongoing and continuous nature of the forward and reverse reactions occurring simultaneously at equilibrium. Although the concentrations of the reactants and products remain constant over time, the individual particles are still reacting, showing a balance between the formation of products and the reformation of reactants.
Step 2
Suggest, with explanations, suitable conditions that the manufacturer could use to maximise the yield and rate of production of propene from propane.
Answer
To maximize the yield and rate of production of propene from propane, the manufacturer could:
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Increase Temperature: Since the forward reaction is endothermic, increasing the temperature will drive the equilibrium position to the right, favoring the formation of propene.
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Increase Propane Concentration: By increasing the concentration of propane, the rate of collision between molecules is enhanced, leading to a higher production rate.
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Use a Catalyst: Implementing a suitable catalyst would lower the activation energy for the reaction, allowing it to proceed faster without affecting the equilibrium position.
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Reduce Pressure: As the reaction produces more gas molecules (2 moles of gas from 1 mole of propane), reducing the pressure would shift equilibrium to the right, favoring the formation of more propene.
Step 3
State the maximum volume of propene, in dm³, formed by the dehydrogenation of 300 dm³ of propane.
Answer
The reaction stoichiometry shows that 1 mole of propane produces 1 mole of propene. Therefore, from 300 dm³ of propane, a maximum of 300 dm³ of propene can be produced, assuming complete conversion.
Step 4
Calculate the maximum mass, in kg, of hydrogen formed in this reaction.
Answer
For every 1 mole of propane that is dehydrogenated, 1 mole of hydrogen gas is produced. The molar volume of a gas at room temperature and pressure is 24 dm³.
From 900 dm³ of propane:
- The moles of propane = ( \frac{900 \text{ dm}^3}{24 \text{ dm}^3/mol} = 37.5 \text{ moles} )
- Therefore, 37.5 moles of hydrogen are produced.
Calculating the mass of hydrogen:
- Molar mass of hydrogen (H) = 1 g/mol
- Mass of hydrogen = ( 37.5 \text{ moles} \times 1 ext{ g/mol} = 37.5 ext{ g} )
- To convert grams to kilograms: ( 37.5 ext{ g} = 0.0375 ext{ kg} )
Thus, the maximum mass of hydrogen formed is 0.0375 kg.