THE ELECTROLYSIS OF AQUEOUS SOLUTION

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Presentation transcript:

THE ELECTROLYSIS OF AQUEOUS SOLUTION Identify cations and anions in various salt solutions Describe the electrolysis of an aqueous solution Predict the products of electrolysis of aqueous solutions Write half equations for discharge of ions at the anode and the cathode

Molten Salts vs. Salt Solutions

Universal indicator-pH by color

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

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

1. Identify all ion present in aqueous solution NaCl Solution Na+ H+ Cl- OH-

Sodium Chloride Solution 1 Carbon-inert Na+ Sodium Chloride Solution H+ Na+ OH- Cl- H+ Cl- Cl- OH- Electrolysis of HCl aqueous

2. Identify ion species moving to cathode and anode electrode NaCl Solution H+ Na + Cl- OH- cathode anode

Electrochemical Series CATIONS ANIONS K+ F- Na+ SO42- Ca+ NO3- Mg+ Cl- Al+ Br - Zn+ I- Fe+ OH- OH- Sn+ Pb+ H+ MORE EASY TO DISCHARGE Cu+ Ag+

NaCl Solution 3. Identify the ion species that will be discharged in cathode and anode NaCl Solution H+ Cl- OH- Na+ cathode anode Choose the ions that are lower in the electrochemical series. They are the ions most easily discharged

4. Write half equation in cathode and anode NaCl Solution H+ Cathode: 2H+ + 2e H2 OH- Anode: 4OH- H2O + O2 + e

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

Salt in SOLUTION Anode Cathode NaCl with UI NaCl Concentrated Observations Salt in SOLUTION Anode Cathode NaCl with UI Gas bubble are released. A colorless gas is formed and the universal indicator turns red Gas bubbles are released. A colorless gas is formed which turns the universal indicator purple NaCl Concentrated Without UI A greenish-yellow gas with a swimming pool smell. The gas turns the blue litmus paper red and then white. Gas bubles are released. A colourless gas which burns with a pop sound is produced.

Dry Cell Battery Interior