If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: Chemistry library>Unit 14

Lesson 6: Electrolytic cells and electrolysis

# Electrolysis of molten sodium chloride

Example quantitative electrolysis problem using molten sodium chloride.  Created by Jay.

## Want to join the conversation?

• thanks so much for your video!
can you create more videos of electrolysis ?especially for ionic solutions i am not clear about the overvoltage! thanks in advance.
• what is the difference between electode and anion
• In terms of electrolysis, an electrode refers to either one of the metal bars used during electrolysis whereas anion is the ion (negatively charged species) present in the solution. For example, Cu^2+ is an ion (cation) whereas Cu metal is the electrode used in electrolysis.
• Is it realistic to ask how much Cl2 is produced at STP given molten NaCl would be at a far higher temperature and/or pressure than 0oC and 1.0atm? Or was STP just chosen for simplicity?
• The Cl₂ would be produced at a different temperature or pressure than STP. But Cl₂ is a gas. You could have calculated its volume at any reasonable combination of P and T.
But we know that 1 mol Cl₂ has a volume of 22.4 L.
STP is a convenient choice of conditions, because it is directly related to an easily-memorized amount (1 mol) of the gas.
• Can you just use the equation Moles = Current * Time / Faraday's Constant * moles electrons for the kind of problem presented around ?
• why do sodium ions gain two electrons instead of one?
• They don't! They gain only one electron.
• Aren't positive ions called cations? Then why does he say "we have liquid sodium ions and liquid chlorine anions"?
• Yes, Na⁺(l) ions are sodium ions and also sodium cations.
It is understood that sodium ions are cations because sodium is a metal.

But Cl⁻(l) ions are chloride ions and also chloride anions.
It is understood that chloride ions are anions because chlorine is a nonmetal.
• How does electrons from chlorine reaches sodium?
Because upto positive terminal its okay as positive terminal is attracting the electrons but what after that , DOES these pass through the electrolyte and if so why aren't they repelled by the negative terminal of the battery?
• Why doesn't sodium react with chlorine gas again ?
• It doesn't react therefore so it can be as a gas
• Why do we write Sodium chloride as "NaCl", why not "ClNa"?
(1 vote)
• In ionic compounds, we generally write the cation (positive ion) first and the anion (negative ion) last.
• I am struggling to understand why a concentrated solution of sodium chloride produces Cl bubbles faster than a dilute solution of sodium chloride that produces Oxygen bubbles.

Scenario 1:
Let's say I add 6 moles of water to 2 moles of sodium chloride to form dilute sodium chloride solution.If I electrolyse this solution, I will eventually get 3 moles of Oxygen gas since 6 moles of oxide ions will react to form Oxygen.

Scenario 2:
On the other hand, let's say I add 2 moles of water to 6 moles of sodium chloride to form concentrated sodium chloride solution.If I electrolyse this solution, I will eventually get 3 moles of Chlorine gas since 6 moles of chloride ions will react to form Cl2.

I don't understand why it is scenario 2 is faster since the same moles of gas (3 moles) is produced in both scenarios. In the first scenario, the water is in high abundance, so lots of it is delocalised to form oxygen and in the second scenario, the chloride ions are in high abundance so there are lots of Chloride ions that delocalise. Since the same amount of both gases are produced (3 moles each), what makes Cl's reaction occur faster than the O's reaction?