A-LevelChemistryGroup 29701/42 · Oct/Nov 2019 · Q513 Marks

Describe fully what would be seen when magnesium and strontium are heated separately in oxygen. magnesium strontium

(a)Describe fully what would be seen when magnesium and strontium are heated separately in oxygen. magnesium strontium[2]
(b)(i)Write an equation for each of the following processes. Include state symbols. calcium is burned in air calcium carbonate is heated strongly[2]
(b)(ii)Calcium hydroxide is formed when water is added to calcium oxide. Calcium hydroxide and calcium carbonate are both used in agriculture. Describe the main benefit of adding calcium hydroxide or calcium carbonate to soil.[1]
(b)(iii)Explain why the Group 2 hydroxides become more soluble down the group.[3]
(c)Describe the observations, if any, that you would make when: • a few drops of NaOH(aq) are added to BaCl2(aq) • a few drops of H2SO4(aq) are added to BaCl2(aq).[2]
(d)Describe and explain how the thermal stability of the Group 2 carbonates varies down the group.[3]

Mark scheme

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

[2] M1: Mg - white flame and Sr - red flame
[2] M2: white solid product once
[2] M1: 2Ca(s) + O2(g) → 2CaO(s) CaCO3(s) → CaO(s) + CO2(g) all substances, balanced
[2] M2: all state symbols
[1] neutralises acid / raises pH
[3] M1: ∆Hlat and ∆Hhyd decrease down group
[3] M2: Hlat decreases / changes more
[3] M3: ∆HSol becomes more exo / more -ve / less endo / less +ve
[2] • no change (for hydroxide) / colourless solution
[2] • white (for sulfate)
[2] • precipitate (for sulfate)
[2] Award 1 mark for two points, award 2 marks for all three points
[3] M1: stability increases / higher T needed for decompose
[3] M2: larger ionic radius
[3] M3: harder to distort / polarise anion / carbonate ion or harder to polarise / weaken C–O or C=O bond.

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.