B.State any one observation for each of the following :
(i) Aqueous solution of caustic soda is added to magnesium sulphate.
(ii) Ammonium hydroxide is added to zinc sulphate.
(iii) Sodium hydroxide solution is added to copper sulphate.
(iv) `AgNO_(3)` solution is added to sodium chloride.
(v) Dilute HCl is added to potassium sulphide.
Answers
(i) Aqueous solution of caustic soda is added to magnesium sulphate.
⇒Magnesium sulphate reacts with sodium hydroxide (NaOH) to form insoluble magnesium hydroxide (a solid).
(ii) Ammonium hydroxide is added to zinc sulphate.
⇒Zinc sulphate reacts with ammonium hydroxide to give ammonium sulphate and zinc hydroxide where ions of sulphate and ammonia are exchanged, hence it is a double decomposition reaction.
(iii) Sodium hydroxide solution is added to copper sulphate.
⇒On adding sodium hydroxide to copper sulphate solution, a pale blue precipitate of copper hydroxide is formed which is insoluble in excess of sodium hydroxide.
(iv) `AgNO_(3)` solution is added to sodium chloride.
⇒When silver nitrate solution is added to sodium chloride solution, then a white precipitate of silver chloride is formed along with a sodium nitrate solution.
(v) Dilute HCl is added to potassium sulphide.
⇒When potassium sulphite is treated with dilute hydrochloric acid, sulphur dioxide gas is evolved along with potassium chloride and water.