Mc Ques Eng Electrolysis

ELECTROLYSIS

Textbook (Book 2) : p.209 – 237

Public Exam Questions :

1. Both rubidium (Rb) and sodium are elements in Group I of the Periodic Table, but rubidium is more reactive than sodium. Hen a rubidium hydroxide solution is electrolyzed using platinum electrodes, hydrogen gas is liberated at the cathode. Which of the following statements is a correct explanation for he phenomenon described above? A. The H+(aq) ion accepts an electron more readily than the Rb+(aq) ion. B. The H+(aq) ion is more mobile than the Rb+(aq) ion and migrates faster to the cathode. C. Rubidium is first liberated, but it reacts immediately with water to give hydrogen gas. D. The concentration of H+(aq) ions is higher than that of Rb+(aq) ions in the rubidium hydroxide solution. (HKCEE 1994)

2. When a substance X is electrolyzed using platinum electrodes, a gas is collected at each electrode. X may be A. silver nitrate solution B. potassium chloride solution C. molten sodium chloride D. molten copper(II) chloride (HKCEE 1994)

3. A student tries to electroplate an iron ring with nickel using the set-up shown below. DIAGRAM Which of the following combinations is correct? Solution X Anode Cathode A. iron(II) sulphate solution iron ring nickel rod B. iron(II) sulphate solution nickel rod iron ring C. nickel(II) sulphate solution iron ring nickel rod D. nickel(II) sulphate solution nickel rod iron ring (HKCEE 1995)

4. Which of the following methods can produce hydrogen? (1) adding zinc to water -1-

ELECTROLYSIS

Textbook (Book 2) : p.209 – 237

(2) electrolyzing dilute sulphuric acid (3) adding magnesium to dilute hydrochloric acid A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1995)

Direction : Q.5 and Q.6 refer to the following experiment. DIAGRAM 5. Which of the following combinations is correct? Gas X Gas Y A. chlorine hydrogen B. chlorine oxygen C. hydrogen chlorine D. oxygen hydrogen 6. Which of the following statements concerning the above experiment? (1) Platinum electrodes should be used. (2) The concentration of Na+(aq) ions around the cathode increases. (3) The solution changes from colourless to pink. A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only (HKCEE 1996)

7. Which of the following substances are commonly found in the waste water produced by electroplating factories? (1) acids (2) alkalis (3) cyanides A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) (HKCEE 1996)

8. During the electrolysis of 1M copper(II) chloride solution using copper electrodes, which of the following changes would occur at the electrodes? -2-

ELECTROLYSIS

A. B. C. D.

Cathode hydrogen liberated copper deposited copper dissolved copper deposited

Textbook (Book 2) : p.209 – 237

Anode chlorine liberated chlorine liberated copper deposited copper dissolved (HKCEE 1997)

9. Consider the electrolysis experiment shown below : DIAGRAM Which of the following statements concerning this experiment is correct? A. The mass of the impure copper rod decreases. B. The blue colour of the copper(II) sulphate solution gradually fades off. C. Oxidation takes place at the impure copper rod. D. The electrolysis process can enhance the corrosion resistance of copper. (HKCEE 1999)

10. Which of the following gases are the major products liberated in the electrolysis of concentrated sodium chloride solution using carbon electrodes? Cathode Anode A. hydrogen chlorine B. chlorine hydrogen C. hydrogen oxygen D. oxygen hydrogen (HKCEE 2000)

Assertive-typed Question 11. 1st statement : During electrolysis, oxidation takes place at the cathode. 2nd statement : Cations accept electrons and are discharged at the cathode. (HKCEE 2002)

12. In the electrolysis of a copper(II) sulphate solution, copper is used as the anode and carbon as the cathode. Which of the following statements concerning this electrolysis is correct? A. The concentration of Cu2+(aq) ions in the solution remains unchanged. B. The concentration of H+(aq) ions in the solution increases. C. O2(g) is liberated at the anode. D. H2(g) is liberated at the cathode. (HKCEE 2003)

13. -3-