A-LevelChemistryChemical bonding9701/41 · May/June 2021 · Q48 Marks

Samples of [Cu(H2O)6]2+ are reacted separately with an excess of aqueous sodium hydroxide or with an excess of aqueous ammonia. Give the following information about these reactions. reaction 1: [Cu(H2O)6]2+ with an excess of aqueous of sodium hydroxide colour and state of the copper-containing species ionic equation type of reaction

(a)(i)Samples of [Cu(H2O)6]2+ are reacted separately with an excess of aqueous sodium hydroxide or with an excess of aqueous ammonia. Give the following information about these reactions. reaction 1: [Cu(H2O)6]2+ with an excess of aqueous of sodium hydroxide colour and state of the copper-containing species ionic equation type of reaction[3]
(a)(ii)reaction 2: [Cu(H2O)6]2+ with an excess of aqueous ammonia colour and state of the copper-containing species ionic equation type of reaction[3]
(b)Copper(I) oxide is added to hot dilute sulfuric acid. A blue solution, X, and a red-brown solid, Y, form. Suggest the identities of X and Y. Name the type of reaction. X Y type of reaction[2]

Mark scheme

Marking points from the official mark scheme (May/June 2021). The mark or mark type is shown in brackets.

[1] M1: blue solid / blue ppt
[1] M2: [Cu(H2O)6]2+ + 2OH- → Cu(OH)2 + 6H2O OR [Cu(H2O)6]2+ + 2OH- → Cu(OH)2(H2O)4 + 2H2O
[1] M3: precipitation / acid-base
[1] M1: dark blue solution / deep blue solution
[1] M2: [Cu(H2O)6]2+ + 4NH3 → [Cu(NH3)4(H2O)2]2+ + 4H2O
[1] M3: ligand exchange / substitution / displacement / replacement
[1] M1: X CuSO4 and Y Cu
[1] M2: type of reaction = redox / disproportionation

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