A-LevelChemistryGroup 29701/41 · May/June 2020 · Q26 Marks
Describe and explain the trend in the solubility of the Group 2 hydroxides down the group.
- (a)(i)Describe and explain the trend in the solubility of the Group 2 hydroxides down the group.[4]
- (a)(ii)Group 2 hydroxides decompose on heating to give the corresponding metal oxide and water vapour. Suggest which of Mg(OH)2 and Sr(OH)2 will decompose at a lower temperature. Explain your answer.[2]
Mark scheme
Marking points from the official mark scheme (May/June 2020). The mark or mark type is shown in brackets.
- [4] M1 solubility increases down the group
- [4] M2 ∆Hlatt and ∆Hhyd both become less exothermic / less negative
- [4] M3 ∆Hlatt changes more (than ∆Hhyd as OH- being smaller than M2+)
- [4] M4 ∆Hsol becomes more exothermic / more negative
- [2] M1 Mg(OH)2 AND Mg2+ has a smaller ionic radii/ Mg2+ has a higher charge density
- [2] M2 OH-ion is polarised/distorted more
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