electrolysis of brine Flashcards
Where is the chlorine gas produced?
And the anode (positive electrode)
Where is the hydrogen gas produced?
At the cathode (negative electrode)
What is the word equation for the electrolysis of brine?
sodium chloride solution ––> hydrogen gas + chlorine gas + sodium hydroxide solution
What happens at the anode in the electrolysis of brine?
The negative chloride ions (Cl^-) are attracted to the positive electrode, where they each lose one electrons as they are oxidised. The chlorine atoms bond together in pairs and are given off as chlorine gas (Cl2)
What is the half equation at the anode for the electrolysis of brine?
2Cl^- (aq) ––> Cl2 (g) + 2e^-
This can also be written as: 2Cl^- (aq) – 2e^- ––> Cl2 (g)
What three products are obtained when an electric current passes through brine?
- chlorine gas
- hydrogen gas
- sodium hydroxide
What happens at the cathode in the electrolysis of brine?
The positive hydrogen ions (H^+) are attracted to the negative electrode, where they gain one electron as they are reduced. The hydrogen atoms bond together in pairs and are given off as hydrogen gas (H2)
What two positive ions are attracted to the cathode in the electrolysis of brine?
Hydrogen and sodium
What element gets discharged from the cathode in the electrolysis of brine?
Hydrogen ions
Why do the sodium ions stay in solution in the electrolysis of brine?
Because they are more reactive than the hydrogen, which is also attracted to the cathode
Why are hydrogen ions formed in brine?
Because of the water being broken down
What is the symbol equation for the breaking down of water?
H2O (l) ⇌ H^+ (aq) + OH^- (aq)
What is the half equation at the cathode for the electrolysis of brine?
2H^+ (aq) + 2e^- ––> H2 (g)
How can they solution around the cathode be tested?
By using indicator, which shows the the solution is alkaline
Why is the solution (sodium hydroxide) around the cathode alkaline?
Because brine contains aqueous ions of Na^+ and Cl^- (from salt), and H^+ and OH^- (from water). The Cl^- (aq) and H^+ (aq) ions are removed during electrolysis. So this leaves a solution containing Na^+ (aq) and OH^- ions, which form a solution of sodium hydroxide, NaOH (aq)
