Question

A student, in carrying out an experiment on the electrolysis of an aqueous solution of copper (II) nitrate, using graphite electrodes, observed that after a time the solution became colorless and bubbles started to be evolved from both electrodes. Explain, giving equations, the reasons for the observations made. Please Help! thanks

Answer 1

@Compassionate @asib1214 @thomaster help?

Answer 2

What would reduce and what would oxidise?

Answer 3

Do you know how to use a reduction potentials table?

Answer 4

no i don't. All is know is that reduction occurs at the cathode while oxidation takes place at the anode.

Answer 5

Okay it's on the right side.

Answer 6

So your reactant is aq. copper nitrate. What would reduce- gain electrons. Aqueous means there is a presence of water- water can either be reduced or oxidised.

Answer 7

Do you know how to deal with voltage?

Answer 8

nope, i haven't reached that stage yet

Answer 9

The reduction - oxidation should be positive.

Answer 10

Copper is an ion.

Answer 11

It is +vely charged so can gain electrons.

Answer 12

It can be reduced.

Answer 13

So it's voltage is?

Answer 14

i'm lost.

Answer 15

Okay. You're familiar with oxidation and reduction right?

Answer 16

yes

Answer 17

Alright. So with problems like this the reactants- the ions within it can reduce or oxidise. Like Cu in copper.

Answer 18

A reduction potentials table tells us which species is reduced and which is oxidised. You see many ions are listed in it, the reducing rxn happens this way ---> (with the table) and oxidising the opposite <---. like switch the arrow.

Answer 19

Getting it so far @Rusty143?

Answer 20

yes i understand

Answer 21

Alright. We use voltage on the right side (the numbers) to determine what exactly will be reduced and oxidised predominantly.

Answer 22

The less negative the voltage, the more that reaction will occur.

Answer 23

If oxidising or reducing.

Answer 24

Now all you need to do is figure out first is what would potentially be reduced or oxidised. It should be on the chart. Any ideas?

Answer 25

Remember an aqueous solution of something contains water- the CuNO3 is dissolved in water.

Answer 26

well at the cathode, it will have, Cu2+ and H+ ions while at the anode, there will be OH- and NO3- ions.so, the Cu2+ will be reduced to Cu and also the H+ will be reduced to H2 (hydrogen gas). In addition, at the anode, the OH- ions will be oxidised to give H2O (liquid) and O2 (oxygen gas). Is this correct?

Answer 27

@AnImEfReaK

Answer 28

@thomaster i'm desperate here.........help?

Answer 29

Hmm well we have water H20 it is in that form so look on the reduction table for just that. Assume it cannot be broken up.