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ICSE Class 9 Chemistry Question 17 of 55

ICSE Questions Set in Previous Years — Question 17

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Question 17

Describe the two colour changes that take place when moist blue litmus is placed in a gas jar of chlorine. What are these colour changes that take place when chlorine water is exposed to sunlight?

Answer

Chlorine turns moist blue litmus red and finally bleaches it i.e., decolourizes it.

When chlorine water is exposed to sunlight, it changes to colourless from greenish yellow. This colour change happens because chlorine reacts with water to form hypochlorous acid which further breaks to form hydrochloric acid and oxygen gas.

Cl2 + H2O ⟶ HClO + HCl

HClO ⟶ HCl + [O]

[O] + colouring matter ⟶ bleached product