A-LevelChemistryGroup 29701/41 · Oct/Nov 2019 · Q612 Marks

The elements in Group 2 include magnesium, calcium, strontium and barium.

(a)(i)Write an equation for the change representing the first ionisation energy of magnesium. Include state symbols. [1][1]
(a)(ii)Write an equation for the reaction of strontium with cold water. Include state symbols. [1][1]
(a)(iii)Describe and explain the trend in reactivity observed in the reactions of these Group 2 metals with cold water. [1][1]
(b)(i)Describe fully what is seen when anhydrous calcium nitrate is heated in a test-tube and decomposition occurs. [1][1]
(b)(ii)Write an equation for the decomposition of calcium nitrate. [1][1]
(b)(iii)Describe and explain the variation in thermal stability of the Group 2 metal nitrates down the group. [3][3]
(c)Describe and explain the variation in the solubility of the Group 2 metal sulfates down the group. [4][4]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2019). The mark or mark type is shown in brackets.

[1] Mg(g) → Mg+(g) + e¯
[1] Sr(s) + 2H2O(l) → Sr(OH)2(aq) + H2(g)
[1] more reactive AND easier to ionise down the group OR more reactive and ionisation energies decrease down the group
[1] brown gas and white solid
[1] 2Ca(NO3)2 → 2CaO + 4NO2 + O2
[3] M1: more stable (down the group) M2: cationic radius increases / charge density of M2+ decreases (down the group) M3: NO3 anion is less polarised / distorted
[4] M1: less soluble / decreases (down the group) M2: ∆Hlatt and ∆Hhyd both decrease / less exothermic down the group M3: ∆Hhyd decreases by more (than ∆Hlatt) M4: ∆Hsol becomes more endothermic / less exothermic

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