09 Apr
2016
Chemistry Tuition Singapore O Level Chemistry Tuition- Salts Common Misconception
Chemistry Tuition Singapore O Level Chemistry Tuition- Salts Common Misconception
Misconception 1
On adding ammonia solution to aqueous copper(II) sulfate, a soluble blue precipitate is formed. (Comment: The error is the phrase “soluble precipitate”.)
Correct Conception 1
On adding ammonia solution to aqueous copper(II) sulfate, a light blue precipitate is formed. The precipitate dissolves in excess ammonia solution.
Misconception 2
All metal ions react with aqueous sodium hydroxide to form precipitates.
Correct Conception 2
Metal ions, such as Na+ and KE, do not form precipitates with NaOH(aq).
Misconception 3
To test for Cl– ions, add hydrochloric acid, followed by silver nitrate solution.
Correct Conception 3
HC1(aq) should not be used, as Cl– ion from HCI(aq) will give a white precipitate with AgNO3(aq). Dilute nitric acid should be used to acidify AgNO3(aq).
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