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NNS chemistry past paper section

In each group, identify the absence which is different from the others and explain your choice. Argon, fluorine, helium, neon b. Nylon, Perspex, polythene, urea-methanol milk of magnesia, soap, vinegar, window cleaner d. Carbon monoxide, hydrogen, methane, nitrogen (8 marks) 2 3. HECK 1996 Cob A, B, C and D are four unlabelled bottles, each containing one of the following reagents: MM ammonia solution, MM ethanol acid, The following scheme is used to identify the four reagents: ?

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Explain What is the reagent in bottle A? Explain why this reagent turns red litmus paper blue. What is the reagent in bottle B? Write a chemical equation for the reaction between his reagent and copper ? Turnings, and a chemical equation for the formation of the brown fumes. Suggest a test to distinguish between the reagent in bottles C and D. (Smelling the reagents in NOT an acceptable answer. ) State the observable change in this test and explain your answer. (8 marks) 3 4 4.

HECK 1998 Q Each of five unlabelled bottles contains one of the following chemicals: 2 M hydrochloric acid 2 M nitric acid 2 M sodium chloride solution 2 M sodium hydroxide solution distilled water Suggest how you would carry out tests to identify the contents of each bottles, using the materials and apparatus listed below. Your answer should include the observation of each test. Copper foil, solid copper(el) carbonate, 2 M copper(el) chloride solution, test tubes and a Bunsen burner (You are Not required to write chemical equations. Answer in the form of flow 5 5.

HECK 1999 The diagram below shows a bottle of chemical waste in a school laboratory. Describe and explain how you would remove kerosene and iron(all) ions from the chemical waste. (You may use any apparatus and chemicals available in a school laboratory. ) (8 marks) 6 6. HECK 2003 ICC Explain why filtration can be used to remove mud particles from muddy water, but Anton be used to remove sodium chloride from sea water. (3 marks) Sea water is a solution while muddy water is a suspension. The size of ions in sea water is much smaller than that of the mud particles in muddy water.

Ions in sea water can pass through pores in filter device while particles cannot. 7. HECK 2004 Q For each of the following pairs of substances, suggest a chemical test to distinguish one substance from the other and state the expected observations. Table salt and white sugar ammonium chloride and potassium chloride dilute sulfuric acid and dilute nitric acid (6 marks) Treat the substances with con. HOSES. White sugar turns black, while slat gives misty fumes. Enoch(s) reacts with Noah(as) to give an alkaline gas, while Kcal(s) does not. Heat the acids with copper metal. Only HON…(as) gives gas bubbles. 8. HECK 2004 ICC A policeman suspected a car driver to have drunk an excessive amount of alcoholic drinks, and used a dichloride breathalyses to conduct a test on the driver’s breath. The result was positive. (I) State the principle underlying the test of ethanol using a dichloride breathalyses. The driver claimed that he had Just rinsed his mouth using ethanol-containing mouthwash. Without sing other instruments, suggest how the policeman could check whether the driver’s claim was valid or not. Explain your answer. (4 marks) Ethanol can reduce Crack-2 (orange) to Car+(green). It) Conduct the test after the driver has thoroughly rinsed his mouth with water. A positive result probably indicates that the driver has drunk. Ethanol is soluble in water. The concentration of ethanol in the breath will drop after the driver has rinsed his mouth. 9. HECK 2005 CIA Calcium is an element in Group II of he Periodic Table. Calcium reacts with nitrogen to form calcium nitride, which is an ionic compound. Electronic diagram of calcium nitride, showing electrons in the outermost shells only. Suggest a test to show that marble is a calcium-containing substance. (3 marks) 8 10.

HECK 2005 Q There are four unlabelled bottles each containing one of the white solids listed below: ammonium chloride, ammonium nitrate, sodium hypochlorite and sodium sulfate Suggest how you would carry out tests to distinguish the four solids from one another. (9 marks) 9 11. HECK 2006 Q An aqueous solution V is known to contain the following four canons: NH+(as), K+ (as), Fee+(as) and Gag+(as) The flow diagram below outlines a series of tests that can be used to detect the presence of two of the above actions in V: Write an ionic equation, with state symbols, for the formation of W from V. 1 mark) Suggest an experimental method that can be used to separate X from W. Name Y. Z still contains two of the above-mentioned canons. Is it possible to show Explain the answer. (2 marks) Based on the above information, suggest a color for V. 10 12. HECK 2007 Q This question involves how to distinguish four unlabelled test tubes, each containing one of the following colorless liquids: ethanol, concentrated sodium hydroxide solution, distilled water, hexane (a) By heating a small amount of each of the colorless liquids to dryness, ONE of the liquids can be distinguished.

Suggest which liquid can be distinguished, and state the observation involved. (2 marks) By applying a flame directly to a small amount of each of the colorless liquids, TWO of the liquids would catch fire. Suggest which two liquids would catch fire. For the two liquids that would catch fire, the observations involved during combustion are different. Suggest the difference in these observations, and explain your answer. Without using other chemicals apart from the above colorless liquids, suggest another method to distinguish the two liquids that would catch fire.


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