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Revision on form 4 chem topics

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  • 1. Revision on form 4 chemistry topics. Section A [42 marks] Answer all questions in this section. The time suggested to answer this section in 60 minutes.1. Table 1 shows the elements P, Q, R, S and T and their proton numbers. The elements are not the actual symbols of elements in Periodic Table. Using these symbols answer the questions below. Elements P Q R S T Proton 6 8 12 17 20 number Table 1 a) State the position of element P in the Periodic Table …………………………………………………………………………………… [1 mark] b) Which elements have the same chemical properties? ……………………………………………………………………………… …… [1 mark] c) Atom Q forms an ion by accepting two electrons i) Write the formula of ion Q. …………………………………………………………………………………… [1 mark] ii) Write the electron arrangement of ion Q ………………………………………………………………………………… … [1 mark] 1
  • 2. d) i) Write the chemical formula of the compound formed when atom R reacts with atom S ………………………………………………………………………………… … [1 mark] ii) State one physical property of compound in c) i) …………………………………………………………………………………… … [1 mark]e) Explain why the size of atom S is smaller compared to the size of atom R ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… [2 marks]f) Atom P and atom hydrogen react to form a molecule [Proton number of hydrogen is 1] i) How many hydrogen atoms in one molecule of the compound formed? …………………………………………………………………………………………… [1 mark] ii) Draw the electron arrangement of the compound formed between atom P and atom hydrogen 2
  • 3. [2 marks]2. Diagram 2 shows electrolytic cell as Cell A and Voltaic cell as Cell B A Zinc Silver Porous pot potpotpot P Q Silver plate Silver nitrate Zinc nitrate solution solution Cell A Cell B Diagram 2By referring to cell A: a) State anode and cathode for electrodes P :…………………….. Q:…………………….. [2 mark] b) State all the ions present in silver nitrate solution …………………………………………………………………………………… [1 mark] c) Write half equation to show reaction at Q ……………………………………………………………………………… …… [1 mark]By referring to cell B: 3
  • 4. d) i) Which metal plate is negative terminal? …………………………………………………………………… …………… [1 mark] ii) Explain your answer in d (i) ……………………………………………………………………………… … [1 mark]e) What is the function of porous pot? ………………………………………………………………………………… … [1 mark]f) State one observation at silver electrode …………………………………………………………………………………… [1 mark]g) State two differences between cell A and cell B: In terms of Cell A Cell B Energy changes Types of electrode [2 marks] 4
  • 5. 3. Table 3 shows the description and observation for two experiments involving two solutions to investigate the role of water in showing the properties of acid Solution B Solution A Experiment Hydrogen chloride in Hydrogen chloride in water chloroform Experiment I Effervescence occurs. Reaction with calcium A colourless gas is liberated No change occur carbonate turns limewater cloudy Experiment II Ammeter does not show Electrolysis using carbon Ammeter shows reading reading electrodes Table 3 a) i) Name the colourless gas liberated during reaction with calcium carbonate in solution A ................................................................................................................ ....... [1 mark] ii) Draw the set-up apparatus in experiment I for solution A 5
  • 6. [2 marks]b) i) Which solution shows acidic property? ............................................................................................................ ........... [1 mark] ii) What is the role of water in solution A? ....................................................................................................................... [1 mark]c) Solution A shows ammeter reading but solution B does not show any reading. Explain why. ......................................................................................................................... ......................................................................................................................... ………………………………………………………………………………………. [3 marks]d) In another experiment, solution B does not show effervescence when reacted with magnesium. Explain ……………………………………………………………………………………… [1 mark]e) What is the effect of dry blue litmus paper on solution B? ………………………………………………………………………………………. 6
  • 7. [1 mark]4. Diagram 4 shows preparation of ammonium chloride and lead(II) sulphate PROCESS I Hydrochloric + Ammonium Ammonium acid hydroxide chloride Solution A + Solution B PROCESS II Lead(II) sulphate Diagram 4Lead(II) sulphate and ammonium chloride are both salts. a) What is meant by ‘salt’? …………………………………………………………………………………… … [1 mark] b) Classify lead(II) sulphate and ammonium chloride into soluble and insoluble salt Soluble salt Insoluble salt [1 mark] 7
  • 8. c) i) Name Process II ……………………………………………………………………………………... [1 mark] ii) Name solution A and solution B Solution A: ……………………………… Solution B : ……………………………… [2 marks]d) Write the chemical equation for the formation of ammonium chloride salt in Process I ……………………………………………………………………………………... [1 mark]e) Describe briefly a test to determine the presence of chloride ion in ammonium chloride solution …………………………………………………………………………………… … 8
  • 9. ……………………………………………………………………………………… ……………………………………………………………………………………… [2 marks]f) In a different experiment, 12.50 cm3 of 0.5 moldm-3 sulphuric acid completely neutralised 25.0 cm3 of sodium hydroxide. 2NaOH + H2SO4  Na2SO4 + 2H2O Calculate the concentration in moldm-3 for sodium hydroxide 9
  • 10. [3 marks] Section B [ 20 marks ] Answer any one question in this section The time suggested to answer this section is 30 minutes5. a) i) What is meant by electrolyte? [2 marks] ii) Explain why solid sodium chloride cannot conduct electricity but molten sodium chloride can. [3 marks] iii) Electrolysis is carried out on a dilute sodium chloride solution using carbon electrodes. Oxygen gas produced at anode and hydrogen gas produced at cathode. Explain how these products are formed. [6 marks] 10
  • 11. b) An experiment was carried out to construct the Electrochemical Series of metals X, magnesium, tin and zinc based on the potential differences between two metals. Table 5 shows the reading of the potential differences and negative electrodes for some pairs of metal. Pairs of metal Potential Negative Cell electrodes difference / V electrodes 1 Zinc and Magnesium 1.61 2 Magnesium and X 1.93 Magnesium 3 Tin and X 0.73 X 4 Zinc and X Zinc Table 5 Based on Table 5 above, answer the questions below: i) Draw a labelled diagram to show how the experiment is carried out in Cell 1 [2 marks] ii) State the negative electrode for Cell 1 and give reason. [2 marks] iii) Determine the potential differences in Cell 4 [2 marks] iv) Arrange the metals X, magnesium, tin and zinc in descending order in the Electrochemical Series. [1 mark] v) Compare the potential difference between Cell 1 and Cell 2 and give your reason. 11
  • 12. [2 marks]6. Tables 6 shows the types of solutions and their basicity. Substances Types of solution Basicity A Strong acid Monoprotic acid B Strong acid Diprotic acid C Strong alkali - Table 6 a) i) What is meant by strong acid? [2 marks] ii) Give one example of each substance A and substance B. pH value of substance B is lower than pH value of substance A at the same concentration, explain. Include in your answer the equations for ionization for both substance A and substance B in water. [6 marks] b) Acid A reacts with 25.0 cm3 of 0.5 moldm-3 of alkali C to produces sodium nitrate and water by neutralization process. i) Suggest what is acid A and what is alkali C. Describe briefly how you would identify the presence of nitrate ion in the laboratory. [6 marks] ii) Describe procedures how to obtain sodium nitrate crystals from the sodium nitrate solutions. [4 marks] 12
  • 13. c) A farmer has a problem with his acidic soil in agriculture. Suggest a substance used to overcome the problem and give reason. [2 marks] Section C (Paper 3) [ 33 marks] Answer all questions in this section The time suggested to answer this section is 60 minutes Diagram 77. Diagram 7 shows two electrolytic cells. Electrolytic cell I uses hydrochloric acid of concentration 0.001 moldm -3 and electrolytic cell II uses hydrochloric acid of concentration 1.0 moldm -3. 13
  • 14. a) State 2 observations at anode and the responding inferences in table 7.1 below. Electrolyti Observations at anode Inferences c cell I II Table 7.1 [6 marks]b) For this experiment, state i) Manipulated variable ……………………………………………………………………… ii) Responding variable ……………………………………………………………………… iii) Constant variable ……………………………………………………………………… [3 marks] 14
  • 15. c) In electrolytic cell I, colourless gas is produced at the anode. In electrolytic cell II, pale yellow gas is produced at the anode. Explain the difference . Cell I : ……………………………………………………………………………………… ……………………………………………………………………………………… Cell II : ……………………………………………………………………………………… ……………………………………………………………………………………… [3 marks]d) Electrolytic cell I is used to carry out the electrolysis of the following solutions. 1.0 moldm-3 sulphuric acid 1.0 moldm-3 nitric acid 1.0 moldm-3 potassium iodide Classify the solutions by completing the table 7.2 below Solutions that produce oxygen at Solutions that do not produce the anode when electrolysed oxygen at the anode when electrolysed Table 7.2 [3 marks]e) i) Draw a labelled diagram to show how to collect gas at anode and cathode in cell I 15
  • 16. [3 marks] ii) What is the product formed at the anode in cell II after the electrolysis is done for 30 minutes? …………………………………………………………………………………. [3 marks]8. One of the purpose of electroplating is to make the appearance of objects become more attractive. Student A used iron spoon as cathode and silver metal as anode. The spoon was successfully electroplated. Student B used iron spoon as anode and silver metal as cathode. The spoon was not electroplated.You are given iron spoon, silver metal and 2 moldm-3 silver nitrate.Referring to statement above, plan an experiment to investigate theposition of electrode at anode or cathode to be used in electroplating ofiron spoon with silver.Your planning must include the following items: (a)Aim of the experiment (b)Statement of the hypothesis (c) All the variables (d)List of materials and apparatus (e) Procedure 16
  • 17. (f) Tabulation of data [17 marks] - END OF QUESTIONS- 17