NEET Chemistry The p-Block Elements (XII) Questions Solved


Account for the following ;

(i) Chlorine water loses its yellow colour on standing.

(ii) BrCl3 is more stable than BrCl5.

(iii) Fluorine does not form oxoacids.

(iv) PCl5 acts as an oxidising agent.

(v) SO2 is an air pollutant.

(i) Cl2 water on standing loses its yellow colour due to the formation of HCl and HOCl. HOCl is unstable and decomposes to HCl. As a result, yellow colour disappears.


  2HOCl 2HClcolourless+O2

(ii) In BrCl3, Br can accommodate three chlorine atoms around it and hence it is stable but in BrCl5, five Cl atoms cannot be accommodated around Br and hence it is unstable.

(iii) Due to high electronegativity and small size F does not form oxoacids.

(iv) In PCl5, the oxidation state of phosphorus is +5. Thus, it cannot increase its oxidation state beyond +5. So PCl5 cannot act as a reducing agent. However, it can decrease its oxidation state from +5 to +3 or to some lower value. Thus, it acts as an oxidising agent.

(v) SO2 is a pungent and irritating gas. It acts as an air pollutant due to the following reasons :

i) It causes throat and eye irritation as it is absorbed readily by respiratory tract.

ii) It combines with moisture forming sulphurous acid. It is then converted into H2SO4. Both these acids cause acid rain and destroy the marble, corrode metals, deteriorate fabrics, paper, leather etc.

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