1. The document discusses the steps to predict the products of electrolysis of aqueous solutions by identifying the ions present, which ions move to the cathode and anode, and which ions will discharge at each electrode. 2. Half reactions are written for the electrolysis of diluted and concentrated hydrochloric acid that show hydrogen ions discharging at the cathode and chlorine or oxygen discharging at the anode. 3. Observations are described for experiments electrolyzing diluted and concentrated hydrochloric acid that are consistent with the predicted half reactions.

1. ANALYSING THE ELECTROLYSIS OF AQUEOUS SOLUTION Write half equations for discharge of ions at the anode and the cathode Predict the product of electrolysis of aqueous solutions

2. - + + - - - - + + + Anions Cations electrolyte Anode ELECTROLYTIC CELL cathode

3. Electrochemical Series Cu + H + Pb + Sn + Na + K + Ca + Mg + Al + Zn + Fe + Cl - Ag + NO 3 - SO 4 2- F - Br - OH - I - CATIONS ANIONS MORE EASY TO DISCHARGE

4. OH - Cl- Carbon H + H + OH - Hydrochloric acid Solution Cl - 1 Electrolysis of HCl aqueous Cl -

5. Step to identify ion in electrolysis of aqueous solution 1. Identify all ion present in aqueous solution 2. Identify ion moving to cathode and anode electrode 3. Identify the ion that will be discharge in cathode and anode 4. Write half equation in cathode and anode

6. Dilute HCl H + Cl - OH - Concentrated HCl H + Cl - OH - 1. Identify all ion present in aqueous solution

7. Diluted HCl H + Cl - OH - Concentrated HCl H + Cl - OH - cathode cathode anode anode 2. Identify ion moving to cathode and anode electrode

8. Diluted HCl H + Cl - OH - Concentrated HCl H + Cl - OH - Choose ion that are lower In the electrochemical series for Diluted HCl and choose ion that are higher In the electrochemical series 3. Identify the ion that will be discharge in cathode and anode cathode anode cathode anode

9. Diluted HCl H + Cathode: 2H + + 2e H 2 OH - Anode: 4OH - H 2 O + O 2 + e Concentrated HCl H + Cathode: 2H + + 2e H 2 Cl - Anode: 2Cl - Cl 2 + 2e 4. Write half equation in cathode and anode

10. STEP TO WRITE HALF EQUATION OF DISCHARGE ION 1. Write reactant and product of reaction 2. Balance the number of atom in both equations 3. Balance the charge of both equation by adding of electron

11. OBSERVATION EXPERIMENT 6.2 Gas bubles are released. A colourless gas which burns with a pop sound is produced. A greenish-yellow gas with a pungent and choking smell is realesed. The gas turns the blue litmus paper red and then white. Concentrated HCl Gas bubbles are released. A colourless gas which burns with a pop sound is produced Gas bubble are released. A colourless gas which relights a glowing splinter is produced DILUTED HCl Cathode Anode SOLUTION

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13. OBSERVATION EXPERIMENT 6.3 COPPER CARBON ELECTRODE The cathode becomes thicker. Copper electrode dissoves into the solution. The anode become thinner. THE INTENSITY OF THE BLUE COLOUR OF THE ELECTROLYTE REMAINS UNCHANGED A reddish-brown solid is deposited on the cathode. Gas bubble are released. A colourless gas which relights a glowing splinter is produced THE INTENSITY OF THE BLUE COLOUR OF THE ELECTROLYTE DECREASE Cathode Anode ELECTROLYTE