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Q.4 Assertion : Fe2O + 2Al → Al2O + 2Fe
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The above chemical equation is an example of displacement reaction.
Reason : Aluminium being more reactive than iron, displaces Fe from its
oxide.

Q.5 Assertion The reaction in which two compounds exchange their ions to form
two new compounds is a double displacement reaction.
Reason : One of the salt produced is insoluble in water.

Subjective questions-

1. A solution of a substance ‘X’ is used for white washing. (i) Name the substance ‘X’
and write its formula. (ii) Write the reaction of the substance ‘X’ named in (i) above
with water.
2. Why is the amount of gas collected in one of the test tubes during electrolysis of
water is double of the amount collected in the other? Name this gas.

3.Why are decomposition reactions called the opposite of combination reactions?
Write equations for these reactions.

4. Write one equation each for decomposition reactions where energy is supplied in
the form of heat, light or electricity.

5. What is the difference between displacement and double displacement reactions?
Write equations for these reactions.

6. In the refining of silver, the recovery of silver from silver nitrate solution involved
displacement by copper metal. Write down the reaction involved.

7. What do you mean by a precipitation reaction? Explain by giving examples.

8. A shiny brown coloured element ‘X’ on heating in air becomes black in colour.
Name the element ‘X’ and the black coloured compound formed.

9. Write two observations each for the following chemical reactions :

(i) Dilute sulphuric acid is poured over zinc granules

(ii) Potassium iodide solution is added to lead nitrate solution

(iii) Lead nitrate is strongly heated in a hard glass test take

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