NCERT Class XI Chemistry Redox Reactions Solutions
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Question : 12
Total: 30
How do you count for the following observations ?
(a) Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
(b) When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?
(a) Though alkaline potassium permanganate and acidic potassium permanganate both are used as oxidants, yet in the manufacture of benzoic acid from toluene we use alcoholic potassium permanganate as an oxidant. Why? Write a balanced redox equation for the reaction.
(b) When concentrated sulphuric acid is added to an inorganic mixture containing chloride, we get colourless pungent smelling gas HCl, but if the mixture contains bromide then we get red vapour of bromine. Why?
Solution:
(a) In neutral medium, KMnO4 acts as an oxidant as follows :
M n O 4 – + 2 H 2 O + 3 e – M n O 2 + 4 O H –
In laboratory, alkaline KMnO4 is used to oxidise toluene to benzoic acid.
In industry alcoholicK M n O 4
1. Cost of adding a base or an acid is avoided as a base (O H –
2. An organic polar solvent, ethyl alcohol, helps in mixing of two reactantsK M n O 4
(b) When a chloride such as NaCl is heated with conc.H 2 S O 4 H 2 S O 4
N a C l + H 2 S O 4
N a H S O 4 + H C l
But when NaBr is heated with conc.H 2 S O 4 H 2 S O 4 B r 2
H 2 S O 4 ( a q )
S O 2 ( g ) + H 2 O ( l ) + [ O ]
N a B r ( s ) + H 2 S O 4 ( a q )
N a H S O 4 ( a q ) + H B r ( g ) 2 H B r ( g ) + [ O ] H 2 O ( l ) + B r 2 ( g )
In laboratory, alkaline KMnO4 is used to oxidise toluene to benzoic acid.
In industry alcoholic
1. Cost of adding a base or an acid is avoided as a base (
2. An organic polar solvent, ethyl alcohol, helps in mixing of two reactants
(b) When a chloride such as NaCl is heated with conc.
But when NaBr is heated with conc.
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