Question

b) Give one example each of a chemical reaction characterised by
1) change in colour
(3) change in state
2) formation of precipitate
(4) evolution of gas.​

Answer 1

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➤ Change in colour:-

☛ The chemical reaction between citric acid and purple coloured potassium permanganate Solution is characterised by a change in colour from purple to colourless.

➤ Change in state :-

☛ The combustion reaction of candle wax is characterised by a change in state from solid to liquid and gas ( because wax is a solid ,water formed by the combustion of wax is a liquid at room temperature whereas Carbon dioxide produced by the combustion of wax is a gas)

➤ formation of precipitate:-

☛ The chemical reaction between potassium iodied and lead nitrate is characterised by the formation of a yellow precipitate of lead iodide.

➤ Evaluation of gas :-

☛ The chemical reaction between zinc and dilute sulphuric acid is characterised by the evolution of hydrogen gas.