(Important Questions) Important Question For CBSE Class X Science Board Examination 2009-10 (Set -2)

Q. 61. Hydrogen gas combines with nitrogen.

1. Hydrogen sulphide gas burns in air.
2. Barium chloride reacts with aluminium sulphate.
3. Potassium metal reacts with water
4. Calcium hydroxide + CO₂
5. Zinc + Silver nitrate
6. Aluminium + Copper chloride
7. Barium chloride reacts with Potassium sulphate.
8. Potassium bromide + Barium iodide
9. Zinc carbonate (heat)
10. Hydrogen + Chlorine
11. Magnesium + HCl
12. Plaster of paris is treated with water

Q. 62. What is corrosion and rancidity?

Q. 63. Why should curd and sour substances not keep  in brass and copper vessels?

Q. 64. Why does dry HCl gas not change the colour of  dry litmus paper.

Q. 65. While diluting an acid, why is it recommended  that the acid should be added to water and not water to the acid.

Q. 66. Do basic solutions also have H­+ ions? If yes, then  why are these basic?

Q. 67. Name the substance which on treating with chlorine yields bleaching powder. Give reaction also.

Q. 68. Name the sodium compound which is used for softening hard water.

Q. 69. Why does distilled water not conduct electricity, whereas rain water does?

Q. 70. Why do acids do not show acidic behaviour in the absence of water?

Q. 71. Plaster of paris should be stored in a moistened-proof container. Explain why?

Q. 72. Give two important uses of washing soda and baking soda.

Q. 73. Milkman adds a very small amount of baking soda to freash milk.

1. Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
2. Why does this milk take a long time to set as curd?

Q. 74. .Why is sodium kept immersed in kerosene oil?

Q. 75. Write equation for the reaction of

1. iron with steam
2. Calcium and potassium with water.

Q. 76. What would you observe when zinc is added to a solution of iron sulphate? Write the chemical reaction that takes place.

Q. 77. What chemical process is used for obtaining a metal from its oxide?

Q. 78. Food cans coated with tins and not with zinc why?

Q. 79. What are amphoteric oxides? Give two examples.

Q. 80. State two ways to prevent rusting of iron.

Q. 81. Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.  Why?

Q. 82. What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?

Q. 83. Would you be able to check if water is hard by using a detergent?

Q. 84. What is hydrogenation? What is its industrial application?

Q. 85. Why do you think the noble gases are placed in a separate group?

Each two marks:

Q.1. Why should magnesium ribbon be cleaned before burning in air?

Q.2. What is a balanced chemical equation? Why should chemical equation be balaced?

Q.3. What does one mean by exothermic and endothermic reactions? Give examples.Oil and fat containing food items are flushed with nitrogen. Why?

Q.4. Why do HCl, HNO₃ etc. show acidic character in aqeous solution while solutions of compounds like alchohol and glucose do not show acidic character?

Q.5. Show the formation of Na₂O and MgO by the transfer of electrons.

Q.6. In the electrolytic refining of a metal M, What would you take as anode, the cathode and the electrolyte?

Q.7. Why sour substances are effective in cleaning the tarnished copper vessels?

Q.8. Draw the structure of the following compounds.

1. Ethanoic acid
2. Bromopentane
3. iii. Butanone
4. Hexanal

Q.9. . How would you distinguish experimently between an alcohol and a carboxylic acid?

Q.10. Why is agitation necessary to get clean clothes?

Q.11. Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?

Q.12. Explain the formation of scum when hard water is treated with soap.

Q.13. Give a test that can be used to differentiate chemically between butter and cooking oil.