Thursday, September 15, 2011

10th FORMATIVE ASSESSMENT-CHEMICAL REACTIONS AND EQUATIONS

CHEMICAL REACTIONS AND EQUATIONS
FORMATIVE ASSESSMENT I 

CBSE QUESTION PAPER I 

MARKS-30 TIME- 70 MINUTES
Instructions:
· Questions : 1 to 5 – 1 Mark each
· Questions : 6 to 9 – 2 Marks each
· Questions : 10 to 13 – 3 Marks each
· Question 14 – 5 Marks
1. On what chemical law, balancing of chemical equation is based?

2. Identify the compound oxidized in the following reaction: H2S (g) + Cl2 ® S (s) + HCl (g)
3. Give an example of photochemical reaction.
4. Name the reaction which forms insoluble salts.
5. Name the product obtained and type of reaction given below: Na2SO4 + BaCl2 ® __ + __
6. Explain the following in terms of gain or loss of oxygen with one example:
a. Oxidation               b. Reduction
7. A copper coin is kept in a solution of silver nitrate for some time, what will happen to the coin and the colour of the solution?
8. Why do we apply paint on iron articles?
9. What happens chemically when quicklime is added to water?
10. What is rancidity? Write the common methods to prevent it.
11. What is corrosion? State the conditions necessary for rusting of iron. How rusting is harmful?
12. Name the type of reactions in the following cases:
a. Garbage producing foul smell
b. Burning of natural gas.
c. Carbon dioxide gas passed through lime water.
13. Blue crystals of copper sulphate on heating in a dry test tube become colourless. Give reasons.
14. a. Why can not a chemical change be normally reversed?
 b. Why is it always essential to balance a chemical equation?
 c. What happens when CO2 gas is passed through lime water and why does it disappear on        passing excess CO2?
 d. Can rusting of iron take place in distilled water? 
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