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Chemistry and Physics some Keypoints/Notepoints (onDemandOnly) !! :)

Ariel Robert

Ariel Robert

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Guys I was just jokin, plus btw im a guy using a fake account to stop the CIE from tracking me... :p
 
knowitall10

knowitall10

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  • Assalamu Alaykum Soldier313 and @everyone who had this doubt (long ago;))
Remember when you had asked that question on P4 as to why when electrolysing some aq comp'ds you get one product that doesn't match the answer of the marking scheme? (I'm really sorry brother xhizors i do not mean to discuss any pp's here-this is a conceptual explanation).
Yeah...well, to you and to anyone who didn't know this:
the electrolysis of aq solutions depends on:
  • the relative electrode potential of the ions
  • the conc of the ions
Considering Electrode Potentials:
The more positive the electrode potential of the cation, the greater the ease of discharge at the cathode. (Look the uploaded photo)
At the anode, using graphite electrodes*, the ease of discharge of the anions follows the order: ( look at uploaded photo)
If the conditions are standard, the conc. of aq. solutions is 1.00mol/dm3 with respect to the ionic comp'd dissolved in water. but the conc of hydrogen and hydroxide ions in solution is very low. as long as the difference in electrode potential values is greater than 0.30V, the predictions are highly likely to occur.
Considering Solution Concentration:
When aq. solutions are electrolysed, the ions are rarely present at conc of 1.00 mol/dm3. For eg. when aq NaCl is electrolysed, chloride ions are discharged at the anode in preference to the hyrdoxide ions. now after looking at that uploaded photo, you'll be like WHAT!!!!! but calm down ;)
This is because chloride ions are present at a much higher concentration than hydroxide ions. The chloride ions fall below the hydroxide ions in the discharge series.
But what happens when we electrolyse an extremely dilute solution?
Again, we find that O2, rather than Cl2 is discharged off at the anode for similar reasons as described above.
Guys/Gals, one thing to note is that The proportion of oxygen increases the more dilute the solution.
*Now my question: I don't understand why the book says graphite electrodes specifically...does it mean inert electrodes?
 

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iKhaled

iKhaled

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anyone knows how to calculate the percentage uncertainty? is there a formula or somethin ?
 
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