Thursday, August 2, 2012


ASSIGNMENT : FIRST TERM (2012-2013)  X - CHEMISTRY                         
CHAPTER: ACIDS AND BASES                       Max Marks: 25
A. Very short answer questions: (1 mark each) (1x 6= 6marks)
1. A calcium compound which is yellowish white powder is used as a disinfectant and also in textile industry. Name the compound. Which gas is released when this compound is left exposed to air ?
2. Which element is common to all acids ?
3. What is common name of water soluble bases ?
4. Write the neutralization reaction between acids and bases in terms of the ions involved.
5. Two solutions A and B have pH values 3.0 and 9.5 respectively. Which of these will turn litmus solution from blue to red and which will turn phenolphthalein from colourless to pink.
6. Name the raw material used for the production of caustic soda.
B. Short answer questions: (2 marks each) (2x5=10)
1. State the chemical property in each case on which the following uses of baking soda are based:
a. as an antacid
b. as a constituent of baking powder
2. Take 5 ml of hydrochloric acid in boiling tube or a conical flask. Add few pieces of zinc granules to it.
a. What do you observe on the surface of zinc granules?
b. Name the gas evolved.
c. What happens when the above gas is passed through soap solution ?
d. What happens when a burning candle is brought near the gas filled bubble ?
3. A housewife found that the cake prepared by her is hard and small in size. Which ingradient has she forgotten to add that would have made the cake fluffy. Give reason.
4. Crystals of a substance changed their colour on heating in a closed vessel but regained it after sometime when allowed to cool down. Name one such substance. Explain the phenomenon involved.
5. How is plaster of paris prepared ? Write the equation of the reaction involved.
C. Short answer questions: (3 marks each)(3x 3= 9)
1. A compound X of sodium forms a white powder. It is a constituent of baking powder and is used in some antacid prescriptions. When heated, X gives out a gas and steam. The gas forms a white precipitate with lime water. Write the chemical formula and name of X and the chemical equation for its decomposition on heating. What is its role in baking powder and in antacids.
2. What is the role of pH in our daily life ?
3. What happens when:
     (a) solid sodium hydrogen carbonate is heated
     (b) chlorine gas is passed through dry slaked lime
     (C) gypsum is heated to a temperature of 373 K.

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