Pure Chem CHS Sec 3 Section B

[Turn Over Name: Index Number: Class: CATHOLIC HIGH SCHOOL End-of-Year Examination Secondary 3 (O-Level Programme) CHEMISTRY 2 October 2024 2 hours 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name, index number and class on all the work you hand in. 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. Section B Answer all questions. Write your answers in the spaces provided. For examiner’s use only: Total / 60 working / units / significant figures −1 if checked The number of marks is given in brackets [ ] at the end of each question or part question. A copy of the Periodic Table is printed on page 8 of Section C. The use of an approved scientific calculator is expected, where appropriate. A maximum of 1 mark will be deducted from your total mark for failure to show your working in calculations and misuse of units and/or significant figures, i.e. failure to quote units where necessary, the inclusion of units in quantities defined as ratios o r quoting answers to an inappropriate number of significant figures. This document consists of 14 printed pages and 2 blank pages. B

2 Section B Answer all questions 1 The names of nine gases are given in the following list. ammonia argon helium hydrogen neon nitrogen monoxide oxygen steam sulfur dioxide Choose gases from the list to answer the questions. Each gas may be used once, more than once or not at all. Which gas (a) relights a glowing splint? ..……………………………………………………………….………………………..……. [1] (b) reacts with sodium hydroxide in a neutralisation reaction? ..……………………………………………………………….………………………..……. [1] (c) turns aqueous acidified potassium manganate(VII) from purple to colourless? ..……………………………………………………………….………………………..……. [1] (d) is a compound made up of diatomic molecules? ..……………………………………………………………….………………………..……. [1] (e) is monoatomic and has the electronic configuration 2,8,8? ..……………………………………………………………….………………………..……. [1] [Total: 5]

3 [Turn Over 2 Z is a covalent substance. In an experiment, a sample of pure solid Z was continuously heated for 9 minutes. Fig. 2.1 shows how the temperature of the sample of pure Z changed over time. (a) What is the melting point of pure Z? ………………°C [1] (b) The sample of pure Z was continuously heated between 2 minutes and 5 minutes. Explain, in terms of attractive forces, why there was no increase in the temperature of the sample of pure Z between 2 minutes and 5 minutes. ..………………………………………………………….…….………………………..……….. ..……………………………………………………………….………………………..……. [1] (c) Describe how the movement of particles of pure Z changed from 0 to 2 minutes. ..……………………………………………………………….………………………..….…….. ..……………………………………………………………….………………………..….…….. ..……………………………………………………………….………………………..……. [2] [Total: 4] Fig. 2.1

4 3 Fig. 3.1 shows the structures of two different forms of carbon, P and Q. (a) Put a tick in one box in each row to show which statements about P and Q are true and which are false. true false P has a giant covalent structure, but Q has a simple molecular structure. P is used to coat drill bits while Q is used as a lubricant. The a toms in both P and Q have the electronic configuration of a noble gas. Both P and Q are elements. Both P and Q have high melting points. [3] (b) Carbon can be reacted with boron to form compound R. A sample of R was found to contain 78.6% boron by mass. Deduce the empirical formula of R. Show your working. [3] [Total: 6] Fig. 3.1 P Q

5 [Turn Over 4 Carbon monoxide is a toxic gas. Fig. 4.1 shows a carbon monoxide detector that can be used at home to alert residents of its presence. The orange spot turns black if there is a high concentration of carbon monoxide in the air. The spot turns black when solid palladium(II) chloride reacts with carbon monoxide and another substance to form palladium metal. PdCl2(….) + ………. (g) + CO(g) → Pd(s) + 2HCl(g) + CO2(….) (a) Complete the above equation by filling in the blanks. [2] (b) (i) Complete Table 4.1 to show the oxidation states of palladium and carbon before and after the reaction. Table 4.1 [2] element oxidation state before the reaction oxidation state after the reaction palladium carbon (ii) Use your answers in (b)(i) to explain why this is a redox reaction. ……………………………………………………………………...……………………….. ……………………………………………………………………...……………………….. ..……………………………..………………………….…………………...……..……. [2] (c) Name the chlorine-containing compound formed in the reaction. ..……………………………………………………………….……………………...…..……. [1] Fig. 4.1 Carbon Monoxide Detector orange spot containing palladium(II) chloride

6 (d) The CO molecule does not completely follow normal bonding rules, although both atoms in the molecule have a stable octet electron arrangement. Complete the ‘dot-and-cross’ diagram in Fig. 4.2 to show the bonding in a molecule of CO. Some of the outer electrons of oxygen have been filled in for you. Show outer electrons only. [2] [Total: 9] C O Fig. 4.2

7 [Turn Over 5 Flerovium, Fl, atomic number 114, was first made in research laboratories in 1998. (a) With reference to the Periodic Table, deduce the number of outer electrons in an atom of flerovium. ..……………………………………………………………….………………………..…….... [1] (b) Two isotopes of flerovium are 286Fl and 289Fl. (i) Define the term isotope. ……………………………………………………………………………………..……. [1] (ii) Complete Table 5.1 to show the number of protons, neutrons and electrons in the isotopes shown. Table 5.1 [2] isotope number of protons number of neutrons number of electrons 286Fl 289Fl (c) It has been suggested that flerovium is a typical metal. Predict whether flerovium will have a higher or lower melting point than oxygen. Explain your answer in terms of bonding and structure. ..…………………………………….………….………………………………………..…..…….. ..………………………………………………..………………………………………...….…….. ..…………………………………….………….………………………………………..…..…….. ..………………………………………………..………………………………………...….…….. ..………………………………………….……….……………………………………..……….... ..……………….…………………………….…………………………………………..…...… [3] [Total: 7]

8 6 Hydrochloric acid and sulfuric acid can be used to make salts. (a) Table 6.1 shows information about the preparation of pure samples of solid salts. Complete the table by filling in the missing information. Table 6.1 name of salt names of reagents used method used to prepare salt method used to obtain solid product from the reaction mixture potassium chloride reagent 1: dilute hydrochloric acid reagent 2: …………………….. …………………….. …………………….. crystallisation lead(II) sulfate reagent 1: dilute sulfuric acid reagent 2: …………………….. …………………….. precipitation …………………….. [4] (b) When excess magnesium was added to a sample of dilute hydrochloric acid, 20 cm 3 of hydrogen gas was produced. In another experiment, excess magnesium was added to a sample of dilute sulfuric acid of the same volume and