NimitMistry13
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Ok so in the electrolysis of sodium chloride, hydrogen forms at the cathode instead of sodium because:
- >Hydrogen is less reactive than sodium<, and the less reactive chemical is produced at the electrode
- >Hydrogen accepts electrons more readily< than sodium

How can hydrogen be less reactive, and also accept electrons more readily? 🤔

those two details awarded separate marks in Q24d in the mark scheme*
(mark scheme* = https://www.ocr.org.uk/Images/537505...me-paper-3.pdf)
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adampinsler
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(Original post by NimitMistry13)
Ok so in the electrolysis of sodium chloride, hydrogen forms at the cathode instead of sodium because:
- >Hydrogen is less reactive than sodium<, and the less reactive chemical is produced at the electrode
- >Hydrogen accepts electrons more readily< than sodium

How can hydrogen be less reactive, and also accept electrons more readily? 🤔

those two details awarded separate marks in Q24d in the mark scheme*
(mark scheme* = https://www.ocr.org.uk/Images/537505...me-paper-3.pdf)
Hey! You will probably have to address the electrochemical series. When the sodium ion gains an electron to form solid sodium, the equilibrium reaction produces a E° value of -2.71V. The more negative the E° value is, the further left the equilibrium would lie, resulting in greater tendency for sodium to remain as an ion. Therefore, hydrogen having more positive E° value (relative to sodium), will undergo reduction at the cathode. Hope this sort of makes sense

Another way to think about this is, being an ion provides higher stability with a fully-filled outer shell. Thus, sodium being more reactive would require much more energy to gain the electron, over hydrogen, as sodium would much prefer to be an ion.
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Roha125
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Because the opposite of reaction is also happening

For reaction element to ion
Na -> Na^+1 + e (faster so more reactive)
H -> H^+1 +e

In electrolysis ion to element
Na^+1 +e -> Na
H^+1 +e -> H (faster so reaches cathode first)

Sodium is more reactive as it can lose electron faster than hydrogen to become ions
So in electrolysis,hydrogen can take electrons faster to become element from ions.

First point of marks is about element->ion
Second is ion->element
(You have misconceptions over here)

Sodium can easily turn to ion but it gets harder for it to become element again compare to hydrogen.So hydrogen reaches cathode as it easier for it to become element
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NimitMistry13
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(Original post by Roha125)
Because the opposite of reaction is also happening

For reaction element to ion
Na -> Na^+1 + e (faster so more reactive)
H -> H^+1 +e

In electrolysis ion to element
Na^+1 +e -> Na
H^+1 +e -> H (faster so reaches cathode first)

Sodium is more reactive as it can lose electron faster than hydrogen to become ions
So in electrolysis,hydrogen can take electrons faster to become element from ions.

First point of marks is about element->ion
Second is ion->element
(You have misconceptions over here)

Sodium can easily turn to ion but it gets harder for it to become element again compare to hydrogen.So hydrogen reaches cathode as it easier for it to become element
hmmm ok i think i get it

so sodium loses electrons more readily than hydrogen
so hydrogen gains electrons more readily than sodium?

thanks again!!
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NimitMistry13
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(Original post by adampinsler)
Hey! You will probably have to address the electrochemical series. When the sodium ion gains an electron to form solid sodium, the equilibrium reaction produces a E° value of -2.71V. The more negative the E° value is, the further left the equilibrium would lie, resulting in greater tendency for sodium to remain as an ion. Therefore, hydrogen having more positive E° value (relative to sodium), will undergo reduction at the cathode. Hope this sort of makes sense

Another way to think about this is, being an ion provides higher stability with a fully-filled outer shell. Thus, sodium being more reactive would require much more energy to gain the electron, over hydrogen, as sodium would much prefer to be an ion.
oh i saw the electrochemical series around when i searched about it 😅
it didn't make much sense on other websites, u explained it WAYYYY better

thank you for the answer 😊
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