Hazel reacted 25.0 cm³ of a 2.0 mol/dm³ hydrochloric acid solution with 2.0 g of an unknown carbonate of formula XCO₃. She titrated the resulting mixture with aqueous sodium hydroxide. The unreacted hydrochloric acid needed 10 cm³ of 1.0 mol/dm³ sodium hydroxide to neutralise it. XCO₃ + 2HCl → XCl₂ + CO₂ + H₂O.

1. aWrite the equation for the reaction between hydrochloric acid and sodium hydroxide. [1]
2. bCalculate the number of moles in 10 cm³ of 1.0 mol/dm³ sodium hydroxide. [1]
3. cState the number of moles of hydrochloric acid that reacted with the sodium hydroxide. [1]
4. dCalculate the number of moles in 25 cm³ of 2.0 mol/dm³ hydrochloric acid. [2]
5. eCalculate the number of moles of hydrochloric acid that reacted with 2.0 g of XCO₃. [2]
6. fCalculate the number of moles of XCO₃ in 2.0 g. [1]
7. gCalculate the mass of 1 mole of XCO₃. [1]
8. hCalculate the relative atomic mass of element X. [2]
9. iIdentify element X from the Periodic Table. [1]

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