Q26 of 152 Page 46

(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.

(a) Oxidation and reduction happening simultaneously in a reaction is called redox reaction.


In the above reaction, copper oxide is reduced to copper whereas hydrogen is oxidized to water.


(b)Magnesium is oxidized; because oxygen is added to magnesium creating MgO.


(c) (i) HCl is oxidized.


(ii)MnO2 is reduced.


(iii)MnO2 is oxidizing agent.


(iv) HCl is oxidizing agent.



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24 Fill in the following blanks with suitable words:

(a) The addition of oxygen to a substance is called ......... whereas removal of oxygen is called.........


(b) The addition of hydrogen to a substance is called ......... whereas removal of hydrogen is called.........


(c) Anti-oxidants are often added to fat containing foods to prevent ..........due to oxidation.

 25 What is an oxidation reaction? Identify in the following reaction

(i) the substance oxidised, and


(ii) the substance reduced:


 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.

 28 (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.