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Write any two observations in an activity which may suggest that a chemical reaction has taken place. Give an example in support of your answer.
The two observations suggest that a chemical reaction has taken place are:
(i) Gas is evolved.
For example, When potassium reacts with water to give potassium hydroxide and hydrogen gas is evolved.
$2K( s) +\ 2H_{2} O( l) \ \rightarrow \ 2KOH\ +\ H_{2} \ \uparrow $
(ii) A precipitate is formed.
For example, When potassium iodide solution is added to a solution of lead nitrate, a yellow precipitate of lead iodide is formed.
$2KI\ ( aq) \ +\ Pb( NO_{3})_{2\ }( aq) \ \rightarrow \ PbI_{2} \ ( s) \ +\ 2KNO_{3} \ ( aq)$
Updated on: 10-Oct-2022
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