Copper is a transition element.

1. (a)(i)Complete the electronic configurations of a Cu⁺ ion and a Cu²⁺ ion. Cu⁺ ion: [Ar] .................................................. Cu²⁺ ion: [Ar] ..................................................[1]
2. (a)(ii)Explain why transition elements have variable oxidation states.[1]
3. (b)(i)Aqueous copper(II) sulfate, CuSO4, contains the [Cu(H2O)6]²⁺ complex ion. A few drops of NH3(aq) are added to CuSO4(aq). Describe any observations made.[1]
4. (b)(ii)Write an equation for the reaction taking place.[1]
5. (c)(i)An excess of NH3(aq) is added to CuSO4(aq). Describe any further observations made.[1]
6. (c)(ii)Write an equation for the reaction taking place.[1]
7. (c)(iii)State the name for the type of reaction taking place.[1]
8. (d)(i)Copper metal can be oxidised by acidified KMnO4. The relevant half-equations and their standard electrode potentials, Eº, are shown. Cu²⁺ + 2e⁻ ⇌ Cu E° = +0.34 V MnO₄⁻ + 8H⁺ + 5e⁻ ⇌ Mn²⁺ + 4H₂O E° = +1.52 V A MnO₄⁻/Mn²⁺ electrode is constructed using 0.0020 moldm⁻³ MnO₄⁻, 1.0moldm⁻³ Mn²⁺ and 1.0moldm⁻³ H⁺. The temperature used is 298 K. Use the Nernst equation to show that the E value for this MnO₄⁻/Mn²⁺ electrode is +1.49V.[2]
9. (d)(ii)An electrochemical cell is constructed using a standard Cu²⁺/Cu electrode and the MnO₄⁻/Mn²⁺ electrode described in (d)(i). Calculate the value of Ecell. Ecell = .................................V[1]
10. (d)(iii)Write an equation for the reaction taking place in the electrochemical cell described in (d)(ii).[1]
11. (d)(iv)Complete the sentences for the electrochemical cell described in (d)(ii). The ................................. electrode is the negative electrode. Electrons flow from the ................................. electrode to the ................................. electrode when the cell is in use.[1]
12. (e)A solution containing [Cu(H2O)6]²⁺ is electrolysed for 5.00 hours using a constant electric current. 0.764 g of copper metal is formed at the cathode. No other reduction reaction takes place. Calculate the electric current, in A, used. Give your answer to three significant figures. current = .................................A[3]