SNGS 2024 TA1

This document consists of 12 printed pages. [Turn over Name: _______________________________ ( ) Class:___________ CHIJ ST NICHOLAS GIRLS’ SCHOOL Secondary 4 Termly Assessment 1 (35 Marks) ____________________________________________________________________________ Chemistry (6092) 2024 50 minutes ____________________________________________________________________________ READ THESE INSTRUCTIONS FIRST Write your name, register number, and class on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams or graphs. Do not use highlighters, glue, correction fluid or correction tape. Answer all questions. Write all answers on the question paper. The use of a scientific calculator is expected, where appropriate. You are reminded of the need for clear presentation in your answers. A copy of the Periodic Table is provided on Page 2. The number of marks is given in brackets [ ] at the end of each question or part question. The total number of marks for this paper is 35. Marks Section A (5) Section B (20) Section C (10) Total

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3 Topics tested: Experimental techniques, mole concept, metals and electric cells. Section A : Multiple choice Questions (5 marks) Answer all questions in this section. Circle the correct answers in the table provided on page 5. 1 Solution X is a mixture of aqueous sodium hydroxide and aqueous sodium carbonate. Which apparatus could be used on its own to determine the number of moles of sodium carbonate present in solution X? A 1 only B 3 only C 1 and 2 D 2 and 3

4 2 The ionic equations for some reactions are as follows: Fe(s) + Cd2+(aq) → Fe2+(aq) + Cd(s) Sn(s) + Pb2+(aq) → Sn2+(aq) + Pb(s) Cd(s) + Sn2+(aq) → Cd2+(aq) + Sn(s) Which of the following pairs will result in a reaction? 1 Sn(s) + Fe2+(aq) 2 Cd(s) + Pb2+(aq) 3 Fe(s) + Pb2+(aq) A 1 only B 2 only C 3 only D 2 and 3 only 3 The diagram shows an electric cell. The electrolyte contains dilute sulfuric acid. Which statement about the cell is correct? A Electrons flow from magnesium to silver via the electrolyte. B Magnesium gives away electrons and gets oxidised but silver takes in electrons and gets reduced. C Magnesium gets smaller and silver remains unchanged in size. D The concentration of magnesium ions increases in the electrolyte and the electrolyte becomes more positively charged.

5 4 Iron forms a few oxides, FeO, Fe2O3 and Fe3O4 . Fe3O4 contains both Fe2+and Fe3+. What is the ratio of Fe2+and Fe3+in Fe3O4? A 1 to 1 B 1 to 2 C 2 to 1 D 3 to 4 5 A sample of brass was added to excess dilute hydrochloric acid. When the reaction has completed the mixture was filtered. What ions would be present in the filtrate? 1. copper(II) ions 2. hydrogen ions 3. chloride ions 4. zinc ions A 1 and 2 B 1 and 3 C 2, 3 and 4 D 1,3 and 4 Answers to section A: Circle the most appropriate answer to each question. 1 A B C D 2 A B C D 3 A B C D 4 A B C D 5 A B C D

6 Section B : Short structure Questions (20 marks) B1 Paper chromatography was used to analyse four unknown vitamins, V1, V2, V3 and V4. Two solvents S1 and S2 were used for the analysis. The mixture of V1 to V4 was initially placed on the V4 position and the chromatography paper was placed in solvent S1. The chromatogram was then dried, rotated anti-clockwise and placed in solvent S2. The results are shown in the chromatogra m below after treatment with a locating agent.

7 Table B1.1 shows the Rf values of some of the known vitamins, A, D, E and K, that are soluble in both solvents S1 and S2. Table B1.1 vitamin Rf value for solvent S1 Rf value for solvent S2 A 0.1 0.7 D 0.6 0.4 E 0.8 0.8 K 0.6 0.2 (a) Explain why the spots in the chromatogram have to be treated with a locating agent. ………………………………………………………………………………...….. ……………………………………………………………………………..…...[1] (b) A student deduced that V1 and V3 each matches a vitamin in Table B1.1. Do you agree? Explain your reasoning. ………………………………………………………………………………..…... ……………………………………………………………………………………. ……………………………………………………………………………...…….. ………………………………………………………………………………….[2] (c) (i) Give a possible reason for the observation recorded for V4 in the chromatogram. ……………………………………………………………………….[1] (ii) Hence, suggest a change to the experiment set-up that will make the identification of V4 possible. ……………………………………………………………………….[1] [Total: 5]

8 B2 Some metals react with cold water and some metals react with steam. Calcium reacts with water as shown. Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g) 40 g of calcium reacts with 100 g of water in a beaker. The initial mass of the mixture is 140 g. At the end of the reaction, there is excess water left and the final mass of the solution obtained was recorded. (a) Calculate the mass of hydrogen gas produced and hence calculate the final mass of the solution recorded. [2] (b) The experiment was repeated with 40 g of barium and 40 g of copper separately. Deduce, without calculation, whether the final mass of solution obtained would be more or less than that in part (a) when the reaction has ended in each experiment. Note that the chemical reactivity of group 2 elements increases down the group. ……………………………………………………………………………….…… ……………………………………………………………………………….…… ……………………………………………………………………………….…… …………………………………………………………………………………… …………………………………………………………………………………[3]

9 (c) Red hot iron reacts with steam. Construct an equation, with state symbols, for the reaction of iron with steam. The oxide formed is Fe3O4. …………………………………………………………………………………[2] [Total: 7] B3 The apparatus shown in Fig. B3.1 is used to heat a metal carbonate. Figure B3.1 (a) (i) The same amount of sodium carbonate, zinc carbonate and copper(II) carbonate are heated separately in the apparatus for one minute. State and explain how you would expect the changes to limewater in each experiment to differ. ………………………………………………………………………….. ………………………………………………………………………….. ………………………………………………………………………….. …………………………………………………………………….……. ………………………………………………………………………….. ………………………………………………………………………..[2]

10 (ii) Construct an equation, with state symbols, for the reaction that occurs when zinc carbonate is decomposed by heat. …………………………………………………………………..……[2] (iii) Complete the table below. State the colour s of the three carbonates and their residues formed during the process. carbonate colour residue when hot residue when cold sodium white white zinc white white copp