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The following energy profile relates to the two reactions 2Cu(s) + O2(g) → 2CuO(s) ΔH = -312 kJ mol⁻¹ 2CuO(s) + 1/2 O2(g) → Cu2O(s) ΔH = -170 kJ mol⁻¹ Enthalpy 2Cu(s) + O2(g) ΔH = -170 kJ mol⁻¹ Cu2O(s) + 1/2 O2(g) → 2CuO(s) ΔH = -312 kJ mol⁻¹ - VCE - SSCE Chemistry - Question 7 - 2008 - Paper 1
Question 7
The following energy profile relates to the two reactions 2Cu(s) + O2(g) → 2CuO(s) ΔH = -312 kJ mol⁻¹ 2CuO(s) + 1/2 O2(g) → Cu2O(s) ΔH = -170 kJ mol⁻¹ Enthalpy 2C... show full transcript
Worked Solution & Example Answer:The following energy profile relates to the two reactions 2Cu(s) + O2(g) → 2CuO(s) ΔH = -312 kJ mol⁻¹ 2CuO(s) + 1/2 O2(g) → Cu2O(s) ΔH = -170 kJ mol⁻¹ Enthalpy 2Cu(s) + O2(g) ΔH = -170 kJ mol⁻¹ Cu2O(s) + 1/2 O2(g) → 2CuO(s) ΔH = -312 kJ mol⁻¹ - VCE - SSCE Chemistry - Question 7 - 2008 - Paper 1
Step 1
Identify the reactions and their enthalpy changes
Answer
The two reactions can be identified along with their respective enthalpy changes:
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Formation of Copper(I) Oxide:
This reaction shows the formation of copper(II) oxide from elemental copper and oxygen, with an enthalpy change of -312 kJ mol⁻¹, indicating that it is exothermic.
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Formation of Copper(I) Oxide:
This reaction indicates the conversion of copper(II) oxide to copper(I) oxide, which also releases energy, shown by a negative enthalpy change of -170 kJ mol⁻¹.
Step 2
Determine the overall enthalpy change
Answer
To find the overall enthalpy change of the complete reaction from 2Cu(s) + O2(g) to Cu2O(s), we must combine the enthalpy changes from both reactions:
Starting with reaction 1, we have:
- Formation of Copper (II) Oxide:
Next, using the reverse of reaction 2 to connect it with the first:
- Conversion of Copper (II) Oxide to Copper (I) Oxide:
Overall enthalpy change is then calculated as follows:
Thus, the overall enthalpy change for the reaction converting 2Cu and O2 to Cu2O is -142 kJ mol⁻¹.