We've been doing electrolysis for quite a while now. I understand what the teacher says, but he hasn't really given us questions on it, so I don't really know what kind of questions to expect in the exam.
If anyone could give any examoles, that would be great :)
thanks, Ifé :shock:
OK. I will try to get some questions sorted out for you.
I assume that you have done electrolysis of molten liquids and solutions and have covered the applications of these such as the extraction of aluminium and the purification of copper.
One important thing you need to be able to do is predict the products of an electrolysis. eg
Can you explain why hydrogen and chlorine are produced, leaving sodium hydroxide solution, when sodium chloride solution is electrolysed?
I'm not sure about chlorine, but is it because chlorine ions are negative, so they go to the anode forming chlorine atoms at the anode.
And is hydrogen formed instead of sodium because sodium is higher up the reactivity series than sodium?
Ok, so what about sodium sulfate solution and potassium nitrate solution?
Both the metals are more reactive than hydrogen, so hydrogen and oxyen are fomed at the anode and cathode, leaving just sodium sulfate or silver nitrate behind??
If you find that this helps you, you may wish to tell your friends about the site. The more people we get to use it, the more likely it is that we can keep the site free to use.
lol, I meant could you give me some more questions that I could answer?
and yeahh I would tell my friends about this site, you've helped me soo much, lol thanks :)
When aluminium is extracted from its ore, electrolysis is used.
What is the main ore of aluminium and what is its chemical name?
How is it electrolysed to produce aluminium? (melting / dissolving in water / dissolving in something else)
Give chemical equations to show what is happening. (Do the best you can because of the problem with chemical equations on this discussion page)
There is one reaction that destroys some of the electrodes. Explain how this happens.
There is a big drive to recycle aluminium. Try to explain why this is a good idea. Group your ideas together into headings such as economic, environmental etc.
A not-very-clever chemist suggests that it would be a good idea to electrolyse aluminium sulfate solution in order to produce aluminium. Try to explain why this is a pretty daft idea.
If these are the kinds of questions you want, great. If you want something different, please let me know.
When aluminium is extracted from its ore, electrolysis is used.
1)What is the main ore of aluminium and what is its chemical name?
2)How is it electrolysed to produce aluminium? (melting / dissolving in water / dissolving in something else)
3)Give chemical equations to show what is happening. (Do the best you can because of the problem with chemical equations on this discussion page)
4)There is one reaction that destroys some of the electrodes. Explain how this happens.
5)There is a big drive to recycle aluminium. Try to explain why this is a good idea. Group your ideas together into headings such as economic, environmental etc.
6)A not-very-clever chemist suggests that it would be a good idea to electrolyse aluminium sulfate solution in order to produce aluminium. Try to explain why this is a pretty daft idea.
If these are the kinds of questions you want, great. If you want something different, please let me know.
We don't do aluminium in our syllabus all we do in detail is purifying copper and electrolising brine. But i'll try to answer the ones I can. lol, but can you please send me questions based on them instead, sorry.
1) bauxite
2) in solution??
3) I'm don't know what solution it wll be in
5) recyclng aluminium means there's less need to purify it, so less money is spent creating the energy needed to purify it.
Recycling copper also means there's less need to mine for copper so less of the environment is ruined by miners nad less animals or people loose their homes, also less waste materials are produced.
6)Aluminium is more reactive than hydrogen, so hydrogen would be formed at the cathide instead and sulfur is never formed at the anode, so oxygen would be formed at the anode, leaving aluminium sulfate behind, so the scientist ends up with basically what he started with in the beginning but without the water; he hasn't achieved his aim.
Sorry, my mistake. I will deal with your answers here first and then get you something to think about on coper and sodium.
1) bauxite YES,ALUMINIUM OXIDE
2) in solution?? MOLTEN IN CRYOLITE
3) I'm don't know what solution it wll be in
5) recyclng aluminium means there's less need to purify it, so less money is spent creating the energy needed to purify it. THE MAIN THING IS THE ENERGY NEEDED TO EXTRACT THE ALUMINIUM BY ELECTROLYSIS. RECYCLING ONLY NEEDS THE ALUMINIUM TO BE HEATED UNTIL IT MELTS. RECYCLED ALUMINIUM IS EXACTLY THE SAME AS "NEW" ALUMINIUM.
Recycling copper also means there's less need to mine for copper so less of the environment is ruined by miners nad less animals or people loose their homes, also less waste materials are produced.
6)Aluminium is more reactive than hydrogen, so hydrogen would be formed at the cathide instead and sulfur is never formed at the anode, so oxygen would be formed at the anode, leaving aluminium sulfate behind, so the scientist ends up with basically what he started with in the beginning but without the water; he hasn't achieved his aim. THE ALUMINIUM OXIDE GIVES ALUMINIUM AT THE CATHODE AND OXYGEN AT THE ANODE. SINCE THE ANODES ARE MADE OF CARBON, THEY REACT TO FORM CARBON DIOXIDE AND SO THE ELECTRODES MUST BE REPLACED EVERY FEW WEEKS.
Now for some better questions.
Can you explain how copper is purified by electrolysis. You should be able to say which substances are placed at each electrode and how they will change when electricity flows. You should include a description of the electrolyte (solution).
Why is it important that the copper is made so pure?
Under what conditions do you electrolyse salt to produce sodium?
Give equations for the reaction at each electrode.
Why is it important to keep the sodium and the chlorine separate as they are produced?
How and why would the products be different if you electrolysed sodium chloride solution?
1)Can you explain how copper is purified by electrolysis. You should be able to say which substances are placed at each electrode and how they will change when electricity flows. You should include a description of the electrolyte (solution).
2)Why is it important that the copper is made so pure?
3)Under what conditions do you electrolyse salt to produce sodium?
4)Give equations for the reaction at each electrode.
5)Why is it important to keep the sodium and the chlorine separate as they are produced?
6)How and why would the products be different if you electrolysed sodium chloride solution?
Hope these are better for you.
1) Impure copper is used as the anode and a thin sheet of pure copper is used as the catjode. The electrolyte used is copper sulfate solution. When electricty flows through the anode the impure copper gets ionised and become Cu(2+)and moves into the solution. All the impurities come out as well and fall to the bottom of the container underneath the anode. The positively charged copper ions are then attracted to the negatively charged pure copper cathode where they gain electrons and become copper ions again. As a result there's a build up of pure copper at the cathode and the amount ofimpure copper at the anode gets smaller.
2)Because the impurities in copper such as gold and silver atoms, negatively affect the conductivity of the copper.
3) In water solution
4) Anode....2Cl- = 2e + Cl2
Cathode....2H+ + 2e = H2
Leaving a solution of Na+ and OH- =sodium hydroxide
5) I don't know...
6) I don't know either...
Lol, thanks they're much better...kinda messed up on the last two though :P
Although, it doesn't say anything in my book about them, I have always wondered why?
I know you are limited by the format of the chat page, but don't use "=" in chemical equations. I get round that problem by using "->" instead.
Q5 If the sodium and chlorine are allowed to come into contact, thye will react to form sodium chloride again.
Q6 You can work this out for yourself using the work you did earlier. Think about which ions are present (Na+, Cl-, H+, OH-), send them to the proper electrodes and then choose which will be liberated. You get hydrogen, chlorine and the sodium hydroxide solution is left behind. These are all useful products and this explains why sodium chloride is electrolysed both as a molten liquid and as an aqueous solution.
Hope this helps. Let me know if you want more questions.
Thank you soo much :) I actually understand the topic now!! I'm just going through the whole syllabus again so I'll probaly need more help, so I'll definitely be back lol :P
Again, thank you sooo much!!
Why do the reactivity of the group 1 atoms increase as you go down the group, but the reactivity of group 7 decreases as you go down the group. I get why it does in group 1, but I don't get why it does in group 7?? :huh:
We've been doing electrolysis for quite a while now. I understand what the teacher says, but he hasn't really given us questions on it, so I don't really know what kind of questions to expect in the exam.
If anyone could give any examoles, that would be great :)
thanks, Ifé :shock:
I assume that you are doing GCSE. Please let me know which board sets your exams and I will try to help you.
thanks, yeah I'm doing my Gcse's and it's AQA :)
OK. I will try to get some questions sorted out for you.
I assume that you have done electrolysis of molten liquids and solutions and have covered the applications of these such as the extraction of aluminium and the purification of copper.
One important thing you need to be able to do is predict the products of an electrolysis. eg
Can you explain why hydrogen and chlorine are produced, leaving sodium hydroxide solution, when sodium chloride solution is electrolysed?
I'm not sure about chlorine, but is it because chlorine ions are negative, so they go to the anode forming chlorine atoms at the anode.
And is hydrogen formed instead of sodium because sodium is higher up the reactivity series than sodium?
There are three questions to ask whenever you try to predict the products of electrolysis.
Question 1 Is it molten (a liquid) or is it a solution?
If it is a molten substance, there are only the two "obvious" ions to deal with. The metal ion goes to the negative electrode (cathode)
eg for molten Lead Chloride
Lead ions go to cathode to make lead metal
Chloride ions (notice the ions are chloride not chlorine)
For solutions, there is the added problem of the H+ ions and the OH- ions that come from the water.
Question 2 Which of the cations (positive ions) gives the least reactive substance?
For the cathode, the least reactive substance is released.
Question 3 Is the salt a halide? In other words, can a halogen be released?
For the anode, a halogen is released if possible but if no halogen is available, oxygen is given off.
eg copper sulfate solution:
Cathode Get copper (less reactive than hydrogen)
Anode Get oxygen (sulfate is NOT a halogen)
Leave in solution: Sulfuric acid (hydrogen ions and sulfate ions)
By the way, this is a very expensive way to make sulfuric acid so is never used for that purpose.
Try these. For each one write the name of the substance produced at the cathode and at the anode. Be careful in the name you use (ide / ine etc).
copper chloride solution
molten lead bromide
sodium sulfate solution
potassium nitrate solution
silver nitrate solution
cathode anode
copper chloride solution copper chlorine
molten lead bromide lead bromine
sodium sulfate solution hydrogen sulfur
(+sodium hydroxide)
potassium nitrate solution hydrogen nitrogen
(+ potassium hydroxide)
silver nitrate solution silver nitrogen
I'm hoping that's right :huh:
Thanks so much for this :)
oh and what's a halogen?
Some were right and some were not. The main problem is that, as you said, you don't know what a halogen is!
A halogen is one of the group seven elements (fluorine, chlorine, bromine, iodine).
A halide is one of the group seven elements in an ion form (fluoride, chloride, bromide, iodide).
So, if you have a chloride in solution you will get chlorine at the anode.
The rule for the anode also means that if you have a sulfate or nitrate, you don't get sulfur or nitrogen.
Anything other than halides will give oxygen at the anode. Sorry I can't give superscripts and subscripts but...
4OH- --> 2 H2O + O2 + 4e-
Try those questions again, now that you know about halogens. (You can use copy and paste to save you typing out the whole lot again.
ok...so what's formed instead of nitrogen or sulfur? and what would be left behind?
Since the nitrate and the sulfate cannot give a holgen, thye arev left behind in the solution.
The hydroxide ions (OH-) are electrolysed instead to release oxygen gas at the anode.
. cathode anode
silver nitrate solution silver oxygen
. (+ nitric acid)
Ok, so what about sodium sulfate solution and potassium nitrate solution?
Both the metals are more reactive than hydrogen, so hydrogen and oxyen are fomed at the anode and cathode, leaving just sodium sulfate or silver nitrate behind??
It is simple it is simple use of electronic particles
Ife, you are correct. Sorry it has taken a while to get back to you.
wyldejonny, I am afraid I don't know what you mean.
However, electrolysis is not as simple as you seem to suggest.
lol, it's ok, thank you so much.
Do you mind giving me some more questions that I could answer?
Thanks, Ife
Please do! That is what I am here for.
If you find that this helps you, you may wish to tell your friends about the site. The more people we get to use it, the more likely it is that we can keep the site free to use.
lol, I meant could you give me some more questions that I could answer?
and yeahh I would tell my friends about this site, you've helped me soo much, lol thanks :)
On electrolysis or some other topic?
Electrolysis :)
OK then..
When aluminium is extracted from its ore, electrolysis is used.
What is the main ore of aluminium and what is its chemical name?
How is it electrolysed to produce aluminium? (melting / dissolving in water / dissolving in something else)
Give chemical equations to show what is happening. (Do the best you can because of the problem with chemical equations on this discussion page)
There is one reaction that destroys some of the electrodes. Explain how this happens.
There is a big drive to recycle aluminium. Try to explain why this is a good idea. Group your ideas together into headings such as economic, environmental etc.
A not-very-clever chemist suggests that it would be a good idea to electrolyse aluminium sulfate solution in order to produce aluminium. Try to explain why this is a pretty daft idea.
If these are the kinds of questions you want, great. If you want something different, please let me know.
We don't do aluminium in our syllabus all we do in detail is purifying copper and electrolising brine. But i'll try to answer the ones I can. lol, but can you please send me questions based on them instead, sorry.
1) bauxite
2) in solution??
3) I'm don't know what solution it wll be in
5) recyclng aluminium means there's less need to purify it, so less money is spent creating the energy needed to purify it.
Recycling copper also means there's less need to mine for copper so less of the environment is ruined by miners nad less animals or people loose their homes, also less waste materials are produced.
6)Aluminium is more reactive than hydrogen, so hydrogen would be formed at the cathide instead and sulfur is never formed at the anode, so oxygen would be formed at the anode, leaving aluminium sulfate behind, so the scientist ends up with basically what he started with in the beginning but without the water; he hasn't achieved his aim.
Sorry, my mistake. I will deal with your answers here first and then get you something to think about on coper and sodium.
1) bauxite YES,ALUMINIUM OXIDE
2) in solution?? MOLTEN IN CRYOLITE
3) I'm don't know what solution it wll be in
5) recyclng aluminium means there's less need to purify it, so less money is spent creating the energy needed to purify it. THE MAIN THING IS THE ENERGY NEEDED TO EXTRACT THE ALUMINIUM BY ELECTROLYSIS. RECYCLING ONLY NEEDS THE ALUMINIUM TO BE HEATED UNTIL IT MELTS. RECYCLED ALUMINIUM IS EXACTLY THE SAME AS "NEW" ALUMINIUM.
Recycling copper also means there's less need to mine for copper so less of the environment is ruined by miners nad less animals or people loose their homes, also less waste materials are produced.
6)Aluminium is more reactive than hydrogen, so hydrogen would be formed at the cathide instead and sulfur is never formed at the anode, so oxygen would be formed at the anode, leaving aluminium sulfate behind, so the scientist ends up with basically what he started with in the beginning but without the water; he hasn't achieved his aim. THE ALUMINIUM OXIDE GIVES ALUMINIUM AT THE CATHODE AND OXYGEN AT THE ANODE. SINCE THE ANODES ARE MADE OF CARBON, THEY REACT TO FORM CARBON DIOXIDE AND SO THE ELECTRODES MUST BE REPLACED EVERY FEW WEEKS.
Now for some better questions.
Can you explain how copper is purified by electrolysis. You should be able to say which substances are placed at each electrode and how they will change when electricity flows. You should include a description of the electrolyte (solution).
Why is it important that the copper is made so pure?
Under what conditions do you electrolyse salt to produce sodium?
Give equations for the reaction at each electrode.
Why is it important to keep the sodium and the chlorine separate as they are produced?
How and why would the products be different if you electrolysed sodium chloride solution?
Hope these are better for you.
1) Impure copper is used as the anode and a thin sheet of pure copper is used as the catjode. The electrolyte used is copper sulfate solution. When electricty flows through the anode the impure copper gets ionised and become Cu(2+)and moves into the solution. All the impurities come out as well and fall to the bottom of the container underneath the anode. The positively charged copper ions are then attracted to the negatively charged pure copper cathode where they gain electrons and become copper ions again. As a result there's a build up of pure copper at the cathode and the amount ofimpure copper at the anode gets smaller.
2)Because the impurities in copper such as gold and silver atoms, negatively affect the conductivity of the copper.
3) In water solution
4) Anode....2Cl- = 2e + Cl2
Cathode....2H+ + 2e = H2
Leaving a solution of Na+ and OH- =sodium hydroxide
5) I don't know...
6) I don't know either...
Lol, thanks they're much better...kinda messed up on the last two though :P
Although, it doesn't say anything in my book about them, I have always wondered why?
Some great answers.
I know you are limited by the format of the chat page, but don't use "=" in chemical equations. I get round that problem by using "->" instead.
Q5 If the sodium and chlorine are allowed to come into contact, thye will react to form sodium chloride again.
Q6 You can work this out for yourself using the work you did earlier. Think about which ions are present (Na+, Cl-, H+, OH-), send them to the proper electrodes and then choose which will be liberated. You get hydrogen, chlorine and the sodium hydroxide solution is left behind. These are all useful products and this explains why sodium chloride is electrolysed both as a molten liquid and as an aqueous solution.
Hope this helps. Let me know if you want more questions.
Thank you soo much :) I actually understand the topic now!! I'm just going through the whole syllabus again so I'll probaly need more help, so I'll definitely be back lol :P
Again, thank you sooo much!!
I have a question.
Why do the reactivity of the group 1 atoms increase as you go down the group, but the reactivity of group 7 decreases as you go down the group. I get why it does in group 1, but I don't get why it does in group 7?? :huh:
I will answer this is in a new thread so that anyone else who is online can see the question and, hopefully, benefit from it.