Write the chemical equation of the reaction with an example each in which the following change has taken place:

(i) Change in colour

(ii) Change in temperature 

(iii) Formation of precipitate.

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1 Answers

(i) Change in colour: Reaction between lead nitrate solution and potassium iodide solution.

Pb(NO3)2(aq)+2KI → PbI2(s)+2KNO3(aq)

In this reaction, colour changes from colourless to yellow.

(ii)Change in temperature: Action of dilute sulphuric acid on zinc.

Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2

In this reaction, heat is evolved

(iii) Formation of precipitate: Action of barium chloride on sodium sulphate.

BaCl2(aq) +Na2SO4(aq) →  BaSO4(s) +2NaCl(aq)

BaSO4(s) - ppt

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