A-Level CIE Chemistry 1.7 Kinetics: Methanol, CH₃OH, is considered t

Question

Methanol, CH₃OH, is considered to be a possible alternative to fossil fuels, particularly for use in vehicles.

Methanol can be produced from fossil fuels and from agricultural waste. It can also be synthesised from carbon dioxide and hydrogen.

(a) Define, with the aid of an equation which includes state symbols, the standard enthalpy change of formation of carbon dioxide.

equation

definition .................................................................................

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(b) Relevant ΔH°f values for the reaction that synthesises methanol are given in the table.

| compound      | ΔH°f / kJ mol⁻¹ |
|---------------|------------------|
| CO₂(g)       | -394             |
| CH₃OH(g)     | -201             |
| H₂O(g)      | -242             |

(i) Use these values to calculate ΔH°reaction for this synthesis of methanol.

Include a sign in your answer.

CO₂(g) + 3 H₂(g) ⇌ CH₃OH(g) + H₂O(g)

ΔH°reaction = …………………………………. kJ mol⁻¹

(ii) Suggest one possible environmental advantage of this reaction. Explain your answer.

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(c) The synthesis of methanol is carried out at about 500K with a pressure of between 40 and 100 atmospheres (between 4 × 10⁶ Pa and 10 × 10⁷ Pa) and using a catalyst. The use of such conditions will affect both the rate of reaction and the equilibrium yield.

In the spaces below, explain the effects of higher temperature, higher pressure, and the use of a catalyst on the equilibrium yield of methanol.

higher temperature
effect ...................................................................................................

explanation .............................................................................................

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higher pressure
effect ...................................................................................................

explanation .............................................................................................

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use of catalyst
effect ...................................................................................................

explanation .............................................................................................

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Methanol, CH₃OH, is considered to be a possible alternative to fossil fuels, particularly for use in vehicles - CIE - A-Level Chemistry - Question 3 - 2012 - Paper 1

Worked Solution & Example Answer:Methanol, CH₃OH, is considered to be a possible alternative to fossil fuels, particularly for use in vehicles - CIE - A-Level Chemistry - Question 3 - 2012 - Paper 1

Define, with the aid of an equation which includes state symbols, the standard enthalpy change of formation of carbon dioxide.

Use these values to calculate ΔH°reaction for this synthesis of methanol.

Suggest one possible environmental advantage of this reaction. Explain your answer.

higher temperature

higher pressure

use of catalyst

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