Excess magnesium was added to 25.0 cm³ of dilute hydrochloric acid: Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g). The hydrogen produced was completely reacted with 2.0 g of copper(II) oxide: CuO(s) + H₂(g) → H₂O(l) + Cu(s). (Ar: Cu 64, O 16, H 1, Cl 35.5)

1. aRewrite the first equation as an ionic equation. [1]
2. bCalculate the number of moles in 2.0 g of copper(II) oxide. [1]
3. cCalculate the number of moles of hydrogen that reacted with the copper(II) oxide. [1]
4. dCalculate the number of moles of hydrochloric acid used to make that amount of hydrogen. [2]
5. eWhat is the concentration of the acid in g/dm³? [2]
6. fA redox reaction occurs between copper(II) oxide and hydrogen. Explain why this is a redox reaction, referring to the changes of oxidation number. [2]
7. gName the oxidising agent. [1]

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