Oxidation and reduction的問題(3)

Tieria

2009-03-08 11:21 pm

1. X is an element. It can form a cation X+ which has an electronic arrangement of 2, 8, 8. Which of the following statements concerning X are correct?
(1) X is a strong reducing agent.
(2) X is in Period 4 of the periodic table.
(3) X burns with a golden yellow flame.

A. (1) and (2) only
B. (1) and (3) only
C. (2) and (3) only
D. (1), (2) and (3)

※ 請列明各點對與錯的原因！※

2. Which of the following substances can be used to distinguish between dilute hydrochloric acid and dilute nitric acid?
(1) Litmus solution
(2) Silver nitrate solution
(3) Sodium carbonate

A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only

※ 請列明各點對與錯的原因！※

3. The leakage problem of a zinc-carbon cell can be solved by
(1) replacing the zinc case with a sheet case.
(2) Enclosing the cell in a plastic case.
(3) Replacing ammonium chloride with potassium hydroxide.

A. (1) only
B. (2) only
C. (1) and (3) only
D. (2) and (3) only

※ 請列明各點對與錯的原因！※

回答 (1)

老爺子

2009-03-09 12:09 am

✔ 最佳答案

1.
The answer is A.

The electronic arrangement of X+ is 2, 8, 8.
Therefore, the electronic arrangement of X is 2, 8, 8, 1. X is potassium.

(1) correct.
X is a group I element (potassium). It has a high tendency to be oxidized to X+, and thus it is a strong reducing agent.

(2) correct.
This is because X has 4 filled electronic shells.

(3) incorrect
Potassium bruns with a lilac flame.

2.
The answer is B.

(1) incorrect
Both dilute hydrochloric acid and dilute nitric acid turn blue litmus solution to red.

(2) correct
Silver nitrate solution gives a white precipitate of silver chloride with dilute hydrochloric acid, but does not react with nitric acid.
Ag+(aq) + Cl-(aq) → AgCl(s)

(3) incorrect
Both dilute hydrochloric acid and dilute nitric acid react with sodium carbonate to give carbon dioxide gas.

3.
The answer is B.

(1) incorrect
The anode reaction of zinc-carbon cell is the oxidation of zinc.
Zn(s) → Zn2+(aq) + 2e-

(2) correct
During the oxidation of zinc, the zinc case becomes thinner and thinner, and finally leaks.
A plastic case can keep all materials of the cell inside the case.

(3) incorrect
The leakage is due to the oxidation of zinc case, but the electrolyte has no effect on the leakage of the cell.
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