A chemical reaction is often accompanied by external indications. State the external indications seen during: [2]
i. Addition of dilute acid to an active metal.
ii. Thermal decomposition of mercury[II] oxide.
Answers
Answer:
A chemical reaction is a chemical change where substances react with each other to form a new substance.
(i) addition of dilute acid to an active metal - The test tube becomes hot and hydrogen gas is evolved, which means heat is produced.
(ii) Addition of dilute hydrochloric acid to silver nitrate - A white coloured precipitate is formed which is AgCl
(iii) Addition of water to quicklime - The solution boils and heat is produced accompanied by a hissing sound.
(iv) Thermal decomposition of mercury oxide - The colour of mercury changes from red to silvery, that is metallic.
Answer:
A chemical reaction is a chemical change where substances react with each other to form a new substance.
(i) addition of dilute acid to an active metal - The test tube becomes hot and hydrogen gas is evolved, which means heat is produced.
(ii) Addition of dilute hydrochloric acid to silver nitrate - A white coloured precipitate is formed which is AgCl
(iii) Addition of water to quicklime - The solution boils and heat is produced accompanied by a hissing sound.
(iv) Thermal decomposition of mercury oxide - The colour of mercury changes from red to silvery, that is metallic.
Explanation: