Question

11 Question (3 points) See page 247 Copper has been used for thousands of years, either as a pure metal or in alloys. It is frequently used today in the production of wires and cables. Copper can be obtained through smelting or recycling. Determine the energy associated with each of these processes in order to recycle 145 mol Cu The smelting of copper occurs by the balanced chemical equation: Cuo(4) + CO(g) – Cu(s) + CO,(g) where AH cuois -155 kJ/mol. Assume the process of recycling copper is simplified to just the melting of the solid Cu starting at 25°C. The melting point of Cu is 1084.5'C with AH - 13.0 kJ/mol and a molar heat capacity, cc, 24.5J/mol C.

Answer 1

Smelting:
CuO(s) + CO(g) ⟶ Cu(s) + CO₂(g)

Part 1:

∆H°_{f (Cu)} = 0 kJ/mol , ∆H°_{f (CO₂)} = -393.5 kJ/mol, ∆H°_{f (CuO​​​​​​​)} = -155 kJ/mol, ∆H°_{f (CO​​​​​​​)} = -110.5kJ/mol

∆H°_rxn = Σ [∆H°_{f (products)}] - Σ [∆H°_{f (reactants)}]
= ∆H°_{f (Cu)} +  ∆H°_{f (CO₂​​​​​​​)} -  ∆H°_{f (CuO​​​​​​​)} - ∆H°_{f (CO​​​​​​​)}
= [0 + (-393.5)] - [-155 + (-110.5)] kJ/mol
= -128 kJ/mol

Enthalpy change associated with smelting 1.10 moles Cu :
∆H = (1.45 mol) x (-128 kJ/mol)
= -185.6 kJ

Hence, enthalpy change for the reaction recovering 1.45 mol Cu is -185.6 kJ

Part 2. Recycling:

i) energy required to convert solid Cu to liquid Cu at 25°C:
q_₁ = n ∆H°_fus
= (1.45 moles) x (13.0 kJ/mol)
= 18.85 kJ

ii) Energy required to heat liquid Cu at 25°C to liquid Cu at 1084.5°C :
q_₂ = n c_p ∆T
= (1.45 mol) x (24.5 J/mol•°C) x (1084.5°C - 25°C)
= 37638.7 J
= 37.64 kJ

Total energy associated with recycling process
= (18.85 + 37.64) kJ
= 56.49 kJ

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