Friday, August 19, 2011
CBSE TEST PAPER SCIENCE & TECHNOLOGY (Class-10) Chapter 3. Metal and Non-metals
1. Explain why the surface of some metals acquire dull appearance when exposed to air for a long time. (2 marks)
2. What are amphoteric oxides? Give examples two amphoteric oxides. (2 marks)
3. State two ways to prevent the rusting of iron. (2 marks)
4. Why is aluminum extracted from alumina by electrolytic reduction and not by reducing with carbon? (2 marks)
5. The reaction of a metal X with Fe2O3 is highly exothermic and is used to join broken railway tracks. Identify metal X. Write the chemical equation of its reaction with Fe2O3. (2 marks)
6. Metal sulphides occurs mainly in rocks and the metal halides occur mostly in seas and lakes. What could be the reason for this difference in behavior? (2 marks)
7. Amit took sulphur powder on a spatula and heated it. He collected the gas evolved byinverting a test-tube over it. (2 marks)
(i) What will be the action of gas an (a) dry litmus paper? (b) Moist litmus paper?
(ii) Write a balanced chemical equation for the reaction taking place.
8. Which gas is produced when diluted hydrochloric acid is added to a reactive metal? Write the chemical reaction. When iron reacts with dilute H2SO4. (2 marks)
9. Why do ionic compounds have high melting points? (2 marks)
10. Define the terms: (3 marks)(i) Mineral(ii) Ore and(iii) Gangue
11. Explain how the following metals are obtained from their compounds by the reaction process:
(i) Metal ‘X’ , which is low in reactivity series.
(ii) Metal ‘Y’, which is middle in reactivity series.
(iii) Metal ‘Z’ which is high up in the reactivity series. (3 marks)
12. Give reasons: (3 marks)
(i) Platinum, gold and silver are used to make jewellery.
(ii) Sodium, potassium and lithium are stored under oil.
(iii) Aluminium is a highly reactive metal, still it is used to make utensil for cooking.
13. (i) What is corrosion of metals? Name one metal which does not corrode and one whichcorrodes on being kept in atmosphere.(ii) How will you show that the rusting of iron needs oxygen and moisture at the same time?
14. Give reasons: (5 marks)
(i) The surface of some metals acquires a dull appearance when exposed to air for a long time.(ii) Sodium is kept immersed in kerosene oil.
(iii) A salt which does not conduct electricity in the solid state becomes a good conductor in molten state.
(iv) Ionic compounds have generally high melting points.
(v) An iron grill is painted frequently.
15. What is an alloy? How is an alloy made? List two purposes of making alloys. Mention the constituents and two properties of each of the following alloys:(i)Stainless steel (ii)Brass(5 marks)