Chem HKCEE1997

2008-04-28 1:29 am

36. Which of the following substances can be used to distinguish between concentrated nitric acid and concentrated sulphuric acid?
(1) sodium carbonate power.
(2) copper turnings.
(3) cane sugar.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1),(2) and (3)
answer:C

37. Which of the following substances would react with sodium hydroxide solution?
(1) ammonium chloride solution.
(2) copper (II) sulphate solution. [點解無拿拿會同NaOH react?]
(3) ethanoic acid.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1),(2) and (3)
answer:D

盡量提供equations及加以解釋。
仲有, (1)點解 filtration 個陣要用水沖下d residue?
(2)咩野chemical 先要用 brown bottle 保存,
potassium permanganate solution 為何要用?

回答 (1)

強

2008-04-28 3:19 am

✔ 最佳答案

(1) sodium carbonate power.>>因為carbonate ion同H ion(姐係Acid in solution form)會出carbon dioxide~~兩者都會出CO2,SO分唔到~~
(2) copper turnings.>CE中,,只有conc.sulphuric acid同dilute/conc nitric acid
同copper metal有reaction~~
3) cane sugar>>conc.sulphuric acid有dehydrating property,而CONC nitric acid沒有,那麼conc.sulphuric acid把cane sugar中的水分子抽出來,再把cane sugar變成carbon~~
C12H22O11 ----> 12C + 11H2O
(2) copper (II) sulphate solution. [點解無拿拿會同NaOH react?]
為什麼沒有??NaOH同copper (II) sulphate solution會出blue precipiate which is Cu(OH)2
(1)點解 filtration 個陣要用水沖下d residue?
因為要remove any impurities on the residue surface~~
2)咩野chemical 先要用 brown bottle 保存,
Conc nitric acid,因佢好易decompose in sunlight~~
potassium permanganate solution 為何要用?<<這個不知道,有沒有高人指點??

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