Mock Paper 2

CHEMISTRY 9729/02 Paper 2 Structured Questions 2 hours READ THESE INSTRUCTIONS FIRST Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. The number of marks is given in brackets [ ] at the end of each question, or part question. Question 1 2 3 4 5 6 Total Marks scored Maximum Marks 12 11 11 12 8 21 75 This document consists a total of 18 printed pages, including this cover page.

Paper by @ijustloveh2chem 2 1 (a) In 1967, scientists around the world met up to determine the standard of the second. Prior to that, the second was not properly standardised across the world. 133Cs atomic clocks were used to determine the standard of the second. When an atom is placed under an electromagnetic field, its valence electrons oscillate at a fixed rate. The rate of oscillation was used to determine the standard of the second. It’s estimated that the margin of error is at 1 second per 1.4 million Earth years. (i) Cs is vaporised to ensure more accurate measurements. The interactions in Cs at room temperature may interfere with the measurements taken. Describe these ‘interactions’ in Cs at room temperature. Refer to the structure and bonding in Cs. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] (ii) As there were many atomic clocks at that time, much of the discussion centred around what element was to be used. 2 of the criteria are listed below: • low number of active electrons • easy to vapourise A student proposed 2 other elements that can be used: Pb and Li. Suggest why these elements are poorer candidates compared to Cs. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] (b) (i) State how the reducing power of the Group 1 metals varies down the group with reference to relevant standard electrode potential values. ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [1]

Paper by @ijustloveh2chem 3 (ii) Explain the variation of the first ionisation energy of the Group 1 metals down the group. ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [1] (c) (i) A student attempted to measure the standard electrode potential of the reduction of the aqueous Cs+ ion to Cs metal directly against a standard hydrogen electrode. Explain why his method would not work. ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… ……………………………………………………………………………………………………… …………………………………………………………………………………………………… [2] (ii) Molten CsF was electrolysed.