Q28 of 152 Page 46

(a) Give an example of an oxidation reaction.

(b) Is oxidation an exothermic or an endothermic reaction?


(c) Explain, by giving an example, how oxidation and reduction proceed side by side.

(a) C (s) + O2 (g) CO2 + Heat

Carbon is oxidized to form carbo dioxide.


(b)Oxidation is an exothermic reaction as heat is given by reaction to the surrounding.


(c)


Copper oxide is reduced to copper element and hydrogen gas is oxidized to Dihydrogen oxide(water).



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26 (a) What is a redox reaction? Explain with an example.

(b) When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidized or reduced? Why?


(c) In the reaction represented by the equation:



(i) name the substance oxidised.


(ii) name the oxidising agent.


(iii) name the substance reduced.


(iv) name the reducing agent.

 27 (a) Define a combination reaction.

(b) Give one example of a combination reaction which is also exothermic.


(c) Give one example of a combination reaction which is also endothermic.

 29 (a) What is the colour of ferrous sulphate crystals? How does this colour change after heating?

(b) Name the product formed on strongly heating ferrous sulphate crystals. What type of chemical reaction occurs in this change?

 30 What is a decomposition reaction? Give an example of a decomposition reaction. Describe an activity to illustrate such a reaction by heating.