Chlorine and hypochlorite的化學問題

Tieria

2009-09-21 7:05 am

1. In which of the following experiments will chlorine be produced?
(1) Adding dilute hydrochloric acid to a chlorine bleach
(2) Electrolysing brine using carbon electrodes
(3) Adding bromine water to potassium chloride solution

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

2. 「chlorine reacts with hot and concentrated sodium hydroxide solution to give sodium hypochlorite and sodium chlorate.」點解錯？

3. Which of the following species are present in aqueous chlorine?
(1) Chlorine molecules
(2) Hypochlorous acid
(3) Hydrogen ions

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

回答 (1)

老爺子

2009-09-21 7:58 am

✔ 最佳答案

1.
The answer is A.

(1) is correct.
2H+(aq) + Cl-(aq) + OCl-(aq) → H2O(l) + Cl2(g)

(2) is correct.
Chlorine is formed at the anode due to the oxidation of chloride ion.
2Cl-(aq) → Cl2 + 2e-

(3) is incorrect.
Bromine is less reactive than chlorine. Therefore, bromine does not react with potassium chloride solution.

2.
When the solution is cold, chlorine reacts with concentrated sodium chloride solution to give sodium chloride and sodium hypochlorite.
(Cold) Cl2(g) + 2NaOH(aq) → NaCl(aq) + NaOCl(aq) + H2O(l)
When the solution is hot, chlorine reacts with concentrated sodium chloride solution to give sodium chloride and sodium chlorate.
(Hot) Cl2(g) + 6NaOH(aq) → 5NaCl(aq) + NaClO3(aq) + 3H2O(l)

3.
The answer is D.

In aqueous chlorine, chlorine reacts with water reversibly.
Cl2(aq) + H2O(l) ≒ H+(aq) + Cl-(aq) + HOCl(aq)
Refer to the equation of the above reaction. All of chlorine molecules (Cl2), hypochlorous acid (HOCl) and hydrogen ions (H+) are present in the solution.

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