ACSBR 16 Electrolysis - Assignment ANS

Anglo-Chinese School (Barker Road) A Methodist Institution Founded in 1886 CHEMISTRY DEPARTMENT OF SCIENCE Name: ANSWERS ( ) Class: SEC 4 ELECTROLYSIS – ASSIGNMENT ALEX LEE/2010 PAGE 1 OF 7 PURE Multiple-Choice Questions [20 Marks] TOTAL SCORE / 30 Write in your selected answer for the multiple-choice questions in the boxes provided. 1 2 3 4 5 6 7 8 9 10 B D B B D C A C C A 11 12 13 14 15 16 17 18 19 20 A B B D A C D D D C 1. The circuit below was set-up, using an unknown substance Q. It was observed that the bulb lit, but there were no decomposition products at the electrodes. What is Q? A aqueous sodium chloride C molten sodium chloride B mercury D sugar solution 2. When the experiment below was set-up, the ammeter showed that no current was flowing. A few drops of dilute sulfuric acid were dissolved in liquid Z and the ammeter then showed that a current was flowing. What could Z be? A aqueous NaOH C ethanol B concentrated NaCl D water

ALEX LEE/2010 PAGE 2 OF 7 3. Two cells, containing substances X a n d Y r e s p e c t i v e l y, were connected in series with a battery and a light bulb, as shown in the diagram below. In which of the following pairs of substances did the bulb light up? in X in Y A aqueous copper(II) sulfate solid lead(II) bromide B aqueous potassium sulfate dilute hydrochloric acid C concentrated hydrochloric acid pure ethanoic acid D concentrated sodium chloride concentrated sugar solution 4. Which one of the following does not yield any gaseous products? electrolyte electrodes A aqueous copper(II) sulfate platinum B aqueous silver nitrate copper C concentrated sodium chloride copper D dilute sulfuric acid platinum 5. A liquid is to be electrolysed, and two test-tubes full of the liquid are placed over carbon electrodes. The diagram below shows the apparatus after some time. Which one of the following could be the liquid undergoing electrolysis? A aqueous CuSO4 C concentrated NaCl B concentrated HCl D dilute H2SO4 6. Electrolysis of molten lead(II) bromide gives lead at the cathode. Why does lead form? A Lead(II) bromide decomposes on heating. B Lead is less reactive than hydrogen. C Positive lead(II) ions are discharged at the cathode. D The anode dissolves to form lead(II) ions. X Y

ALEX LEE/2010 PAGE 3 OF 7 7. Four electrolysis experiments, each using aqueous copper(II) sulfate as the electrolyte, were set-up as shown below. In which of these four experiments did the concentration of the copper(II) sulfate electrolyte remain constant? A C B D 8. In which one of the following instances is there no change in the pH of the solution during electrolysis? A concentrated sodium chloride solution between platinum electrodes B copper(II) chloride solution between platinum electrodes C copper(II) sulfate solution between copper electrodes D dilute su