2021 SAJC Prelim P1 Answer

ST ANDREW’S JUNIOR COLLEGE JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CLASS 2 0 S CHEMISTRY Paper 1 Multiple Choice 9729/01 16 September 2021 1 hour Additional Materials: Multiple Choice Answer Sheet Data Booklet READ THESE INSTRUCTIONS FIRST Write in soft pencil. Do not use staples, paper clips, glue or correction fluid. Write your name and class on the Answer Sheet in the spaces provided. There are thirty questions on this paper. Answer all questions. For each question there are four possible answers A, B, C and D. Choose the one you consider correct and record your choice in soft pencil on the separate Answer sheet. Each correct answer will score one mark. A mark will not be deducted for a wrong answer. Any rough working should be done in this booklet. The use of an approved scientific calculator is expected, where appropriate. This document consists of 15 printed pages.

1 Which of the following contains the same number of particles as 16 g of oxygen atoms? A The number of molecules in 24 dm3 of Cl2 under room conditions B The number of ions in 1 dm3 of 1 mol dm-3 aqueous HCl C The number of atoms in 111.6 g of Fe D The number of formula units of 29.25 g of NaCl Ans: A L = 6.02 X 10-23 mol-1 No. of atoms = 16/32 X 2 X L = 1L molecules A - No. of molecules = 24/24 X 1 X L = L molecules B – No. of ions = 1 X 1 X 2 = 2L ions C – No. of atoms = 111.6/ 55.8 X L = 2L atoms D – No. of formula unit = 29.25/58.5 X L = 0.5 L formula unit 2 The first eight ionisation energies of an element Q (in kJ mol–1) are as follows: 966, 1950, 2730, 4850, 6020, 12300, 15400, 18900 Which of the following statements about element Q is correct? A It can form a basic oxide. B It can form a chloride with the formula QCl5. C It has an even number of protons in its atom. D It can form a chloride that is trigonal planar in shape. Ans: B The increase between the fifth and sixth IE is the largest. Hence, there is 5 valence electrons. Hence, the formula is QCl5. 3 A 2.0 g sample containing 0.0130 mol of organoboron compound, with the formula CxHyBOz, was burnt in an excess of oxygen. 4.58 g of CO 2 and 1.76 g of H 2O were produced. What is the molecular formula of the organoboron compound? A CH2BO2 B C8H7BO2 C C8H15BO2 D C9H15BO Ans: C No. of moles of carbon in sample = 4.58/44 = 0.104 No. of moles of H in sample = 1.76/18 x 2 = 0.196 Value of x = 0.104/0.0130= 8 Value of y = 0.196/0.0130= 15 Mr of sample = 2/0.0130=154 Value of z = (154-96-15-10.8)/16=2

Molecular formula is C8H15BO2. 4 Beams of charged particles travelling at the same speed from different sources are subjected to an electric field in two different experiments. In the first experiment, protons are deflected by an angle of +12o. In another experiment under identical conditions, particle X is deflected by an angle of 4o. What could be the composition of particle X? protons neutrons e