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Tuesday, September 20, 2011

10th science Chemistry-CHEMICAL REACTIONS AND EQUATIONS

CHEMICAL REACTIONS AND EQUATIONS
FORMATIVE ASSESSMENT I
Q. 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?
FORMATIVE ASSESSMENT I
Q. PAPER II 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. Burning of a candle is a chemical change; where as melting of a candle wax is
a chemical change. Why?
2. What is a reducing agent?
3. What is the chemical formula of rust?
4. What is the role of catalyst in a chemical change?
5. Why does stale food give a bad smell and bad taste?
6. What are the 2 important conditions of a balanced ionic equation?
7. Why does the blue colour of Copper sulphate solution start fading when a Zinc rod is dipped in it. Write its equation.
8. Give 2 examples from everyday life situations, where redox reactions are taking place.
9. Can we place Silver nitrate in an iron vessel? Why or why not?
10. What types of reactions are represented by the following? Also give reason the
same. (i) A + B → C
(ii) A + BC → AC + B
(iii) AB + CD → AD + CB
11. What is the relationship between oxidation and oxidising agent in a redox
reaction? Write an example to show this relationship.
12. What is corrosion? Why do aluminium sheets not corrode easily? Name any 2
methods to prevent corrosion.
13. Discuss the importance of decomposition reactions in metal industry.
14. (i) Give one example where corrosion is an advantage rather than
disadvantage.
(ii) What is the difference between displacement reaction and double
displacement reaction with suitable example?
(iii) Write 2 limitations of a chemical reaction.

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