A-LevelChemistryGroup 29701/21 · Oct/Nov 2022 · Q29 Marks

Magnesium shows reactions typical of a Group 2 metal.

(a)Draw a labelled diagram to show the bonding in magnesium metal.[2]
(b)(i)Fig. 2.1 shows some reactions of magnesium and its compounds. [Figure 2.1] Identify the other products of reactions 1 and 2. reaction 1 reaction 2[2]
(b)(ii)Reaction 3 is used to form a precipitate of Mg(OH)2 from MgCl2(aq). State why Ca(OH)2(aq) would not form a precipitate of Ba(OH)2 from BaCl2(aq).[1]
(b)(iii)State the type of reaction that occurs in reaction 4.[1]
(c)1 cm³ of MgCl2(aq) is placed in a test-tube. A few drops of AgNO3(aq) are added, followed by 1 cm³ of dilute NH3(aq). State in full what is observed in this experiment.[2]
(d)When 1 cm³ of MgCl2(aq) is added to 1 cm³ of Br₂(aq) in a test-tube, the solution remains orange. Explain this observation.[1]

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Mark scheme

Marking points from the official mark scheme (Oct/Nov 2022). The mark or mark type is shown in brackets.

[1] M1 diagram showing minimum of 4 particles (in total in two rows) (circles) • circles containing Mgn+ do not have to be labelled • must be labelled as 'ion' OR empty circles / circles with Mg must be labelled + ion / positive ion/cation / Mgn+ AND • circles surrounded by electrons shown as e-/- OR in an area around the circles labelled as 'electrons' OR little circles labelled electrons OR electrons drawn only on perimeter of structure
[1] M2 label/legend showing delocalised electrons
[1] reaction 1 = hydrogen / H2
[1] reaction 2 = carbon dioxide / CO2 AND water / H2O
[1] Ba(OH)2 is soluble (in aqueous solution) / solubility of Group 2 hydroxides increases down group
[1] thermal decomposition
[1] white ppt/solid /
[1] solid (re)dissolves (on addition of NH3)
[1] bromine / Br2 is not a strong enough / (too) weak as a oxidising agent (to oxidise chloride / Cl-) owtte / Bromine / Br2 cannot oxidise chloride (ion) / Cl-

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