(a) What is a redox reaction? Explain with example.(b) When a magnesium ribbon burns in air with a dazzling flame and forms a white ash, is magnesium oxidised or reduced? Why?(c) In the reaction represented by the equation:MnO₂ + 4HCl ----> MnCl₂ + 2H₂O + Cl₂ (i) name the substance oxidised.      (ii) name the oxidising agent.(iii) name the substance reduced.    (iv) name the reducing agent.

(a) A redox reaction is one in which oxidation and reduction occur simultaneously in the reaction, i.e if one substance is reduced the other is oxidised.

     $ZnO \ +\ C\ \rightarrow \ Zn + CO $

In the above reaction, C is oxidised as it has gained oxygen to form CO. and ZnO is reduced as it has lost oxygen to form Zn.

(b) When a magnesium ribbon burns in air with a dazzling flame and forms white ash,  magnesium is oxidised because oxygen is added to magnesium.

     $2Mg\ ( s) \ +\ O_{2}( g) \ \rightarrow \ 2MgO\ ( s)$

(c) $MnO_{2} \ +\ 4HCl\ \rightarrow \ MnCl_{2} \ +\ 2H_{2} O\ +\ Cl_{2} \ $

1. The name of the substance oxidised- HCl is oxidised to Cl₂  
2. The name of the oxidising agent- MnO₂ 
3. The name the substance reduced -MnO2  is reduced to MnCl₂. 
4. The name of the reducing agent- HCl.

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Updated on: 10-Oct-2022

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