chemistry F.5 10 points

用戶90065

2009-03-15 2:22 am

1. Which of the following substances will form a precipitate with calcium hydroxide solution?
(1) sodium sulphur solution
(2) zinc nitrate solution
(3) carbon dioxide
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
2. Which of the following solutions will form a white precipitate with potassium hydroxide solution?
(1) calcium nitrate
(2) copper(II) chloride
(3) zinc sulphate
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
3. Which of the following methods can be used to distinguish between sodium chloride solution and zinc nitrate solution?
(1) adding acidified silver nitrate solution
(2) adding a magnesium ribbon
(3) adding potassium hydroxide solution
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
4. Which of the following statements are incorrect?
(1) acids do more damage to the skin and eyes than alkalis.
(2) potassium hydroxide is often calles caustic soda.
(3) dilute sodium hydroxide solution gives a whate precipitate with zinc nitrate while concentrated sodium hydroxide solution does not.
A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)
5. first statement: When a piece of copper metal is added to dilute sulphuric acid, the solution turns blue.
second statement: Copper reacts with dilute sulphuric acid to form blue copper(II) sulphate solution.
6. first statement: Solid citric acid does not turn moist blue litmus paper red.
second statement: Solid citric acid does not contain mobile ions.
(Please answer the questions with explanation, THANKS!)

回答 (1)

六呎將軍

2009-03-16 6:33 pm

✔ 最佳答案

(1) All of them will precipitate with calcium hydroxide solution.
For (1), calcium sulphate is insoluble in water.
For (2), zinc hydroxide is insoluble in water.
For (3), calcium carbonate is insoluble in water.
(2) Copper(II) hydroxide is blue in colour. So ans is (1) and (3) only .
(3) For (1), insoluble silver chloride will be formed for sodium chloride but no observable change for zinc nitrate.
For (2), no observable change for sodium chloride but zinc metal displaced for zinc nitrate.
For (3), no observable change for sodium chloride but white precipitate formed for zinc nitrate.
Ans: (1), (2) and (3)
(4) For (1), incorrect since alkalis can corrode deeper into skin than acids.
For (2), correct as caustic refers to basic substances.
For (3), correct since zinc hydroxide re-dissolves in excess sodium hydroxide solution.
Ans: (2) and (3) only
(5) Stmt 1: Incorrect since dilute sulphuric acid cannot oxidize metals lower than H in ECS.
Stmt 2: Also incorect.
(6) Stmt 1: Correct since all acids exhibit its acidic properties only when dissolved in water.
Stmt 2: Correct and it is an explanation for stmt 1.

參考: Myself

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