Interesting questions (chem)

[bomb]

Explain why electrolysing a dilute solution of sodium chloride is more efficient in producing hydrogen than just electrolysing pure water.

Pure water is not so conductive, electrolysing NaCl would be faster.....I think :S

Edit: now it's right!

[Martoman]

First part is right

[scocliffe09]

you have lots more charged ions floating in NaCl (aq) than you do in water --> charge is carried more effectively --> electrolysis is more efficient

[bomb]

Yup pure water has low [H30+] [OH], so conductivity is lowwww.

[m@tty]

There are very few ions in pure water, so the current is very low and hence the electrolysis is slow. The addition of NaCl puts many more ions in solution, conducts the charge better thus making the electrolysis more efficient.

[Martoman]

yepppppp

[Martoman]

Sulfuric acid is a strong oxidant with the following equation:



A 1M solution of sulfuric acid is electrolysed using inert electrodes. Explain why the product at the cathode is hydrogen and not sulfur dioxide.


(not sure if this is on the course but) Consider the reactions and equilibrium constants at a certain temperature shown below.





Value of a is?

[Mao]

yepppppp

But no one has mentioned why there need to be ions in the solution for electrolysis to occur.. Anyone?

[Martoman]

ions need to be in the solution or in the electrolyte so as to balance the charge so there isn't some massive build up of it. Also, to conduct electrocity there must be charged particles in solution.

[Mao]

ions need to be in the solution or in the electrolyte so as to balance the charge so there isn't some massive build up of it. Also, to conduct electrocity there must be charged particles in solution.

More importantly, transportation of ions in the solution must be possible so polarization does not occur. Electrostatic repulsion is a very strong force, thus the rate of reaction is often limited by the transportation rate of ions in the electrolyte. The transportation rate increases as the ion concentration increases, and also as the temperature increases, and also if the solution is constantly stirred.

[toshibaj]

Sulfuric acid is a strong oxidant with the following equation:



A 1M solution of sulfuric acid is electrolysed using inert electrodes. Explain why the product at the cathode is hydrogen and not sulfur dioxide.


(not sure if this is on the course but) Consider the reactions and equilibrium constants at a certain temperature shown below.





Value of a is?

No idea about the sulfuric acid one.

But a = 5/2

[Martoman]

yep  a is right  :angel:

ions need to be in the solution or in the electrolyte so as to balance the charge so there isn't some massive build up of it. Also, to conduct electrocity there must be charged particles in solution.

More importantly, transportation of ions in the solution must be possible so polarization does not occur. Electrostatic repulsion is a very strong force, thus the rate of reaction is often limited by the transportation rate of ions in the electrolyte. The transportation rate increases as the ion concentration increases, and also as the temperature increases, and also if the solution is constantly stirred.

I thought massive build up encapsulated polarization just not as big boy. Relating it to the rate was pretty sexy though

[kenhung123]

Polarisation means the positive charge one the oxidation anode is too great and negative charge e's would be stuck on and won't flow right?