Chemistry Past Paper

Section A (Answer ALL questions in this Section.)

1. Rubidium (Rb) and potassium belong to the same group in the Periodic Table. The relative atomic mass of rubidium is larger than that of potassium. (a) Explain whether rubidium is more reactive than potassium. (b) Write a chemical equation for the reaction between rubidium and water. (State symbols should be given.) (c) Suggest how rubidium can be stored safely in the laboratory. (d) Suggest ONE safety precaution for handling rubidium in the laboratory.
(5 marks)

|1. |(a) |Rb is more reactive than K because Rb can give away/donate/release its (outermost) electron more | | |
| | |easily/readily. | |1 |
| | |or, Rb can form ion/cation/positive ion more easily/readily. | |(1) |
| | |or, The strength of metallic bond between Rb atoms is weaker than that between K atoms/Rb can atomize more | | |
| | |readily than K. | |(1) |
| | |(DO NOT accept Rb has one more electron shell than K/Rb atom is larger than K atom/Rb is below K in the | | |
| | |Periodic Table.) | | |
| |(b) |[pic] | |1+1 |
| | |or, [pic] | |(1+1) |
| | |(Formulae of reactants and products must be correct; award 1 mark for a balanced equation and 1 mark for | | |
| |