Chemistry Doubts: IGCSE Paper 3

[ThatReallyReallyWeirdDude]

Paper 6 is over. Now it's time to worry about Paper 3.
Post any doubts here, and I'll answer them ​

 

[EpicLol]

I need help on like the basic stuff like colors of different stuff, general equations, types of reactions, rules/why and how stuff react.....and the equilibirum etc....
Plz help
Thx a lot!!!!!!

 

[EpicLol]

And help me on cathodic and scrificial protection plz...thx

 

[ThatReallyReallyWeirdDude]

I need help on like the basic stuff like colors of different stuff, general equations, types of reactions, rules/why and how stuff react.....and the equilibirum etc....
Plz help
Thx a lot!!!!!!

That's a lot. What you need is notes; this thread is for small doubts and your thing covers entire chapters!
The attached file is somethign I wrote about reversible reactions.
A penguin I know wooowooowoo is compiling notes. http://www.xtremepapers.com/communi...uide-according-to-syllabus.16647/#post-289365I'm helping him a bit.
Good luck! Check the syllabus!

 

[Abu mota]

I don't understand the hydrogen fuel cell, I think that the main problem is that they never adk about it and I don't know how will they ask us or what I should learn about them.

 

[Maz]

I don't understand the hydrogen fuel cell, I think that the main problem is that they never adk about it and I don't know how will they ask us or what I should learn about them.

All you have to know is that

-In the fuel cell, hydrogen (or methane), is put along with oxygen and made to react via an externel circuit to provide electricity.
-They are expensive to set up but provide a steady source of electricity.

 

[ThatReallyReallyWeirdDude]

All you have to know is that

-In the fuel cell, hydrogen (or methane), is put along with oxygen and made to react via an externel circuit to provide electricity.
-They are expensive to set up but provide a steady source of electricity.

Of course, the advantages and disadvantages of using Hydrogen as a fuel via combustion apply here too.

 

[Manobilly]

What are your doubts ,what kind of questions?

 

[lol]

I don't understand the hydrogen fuel cell, I think that the main problem is that they never adk about it and I don't know how will they ask us or what I should learn about them.

fuel cell is a method of generating electricity using hydrogen and oxygen. it has appeared in 2010 m/j 32 if im not wrong.
its pretty simple, hydrogen is supplied to the cell and so is oxygen.
at the ANODE, the negative electrode, hydrogen molecules are oxidised to H+ ions.
at the CATHODE, the positive electrode, oxygen molecules are reduced to O2- ions.
they then react to form water.
2H+ + o2- -> H20 (i think, someone please confirm)
advantages: water is renewable, only water is produced, so nonpollutant.
disadvantages: hydrogen is difficult to store and transport, is flammable.

remember, in an electrolysis, cathode is negative and anode is positive.
but in an electrochemical/fuel cell, anode is negative and cathode is positive.
the reasons for this switch are because oxidation ALWAYS takes place at anode and reduction ALWAYS takes place at cathode.
someone please confirm the final equation for me, hope this helped

 

[lol]

 

[ThatReallyReallyWeirdDude]

I think that final equasion is wrong but I don't have the fuel cell worksheet which our teacher gave us.
JimmyCarter do you have it?

 

[ThatReallyReallyWeirdDude]

Don't need to know that much details.
QUote from syllabus:
"Describe the use of hydrogen as a
potential fuel reacting with oxygen to
generate electricity in a fuel cell (details
of the construction and operation of a fuel
cell are notrequired)"

 

[JimmyCarter]

I think that final equasion is wrong but I don't have the fuel cell worksheet which our teacher gave us.
JimmyCarter do you have it?

no i lost it -.- its useless anyways

 

[Penalopi]

Is Naphta used for a fuel or just for heating systems? And which fraction exactly does it come out from? The book says nothing about it!

 

[ZainH]

I'll be lurking this thread 24/7 on tuesday.
Might even have a few doubts tomorrow.. but mostly tuesday x)

 

[Penalopi]

fuel cell is a method of generating electricity using hydrogen and oxygen. it has appeared in 2010 m/j 32 if im not wrong.
its pretty simple, hydrogen is supplied to the cell and so is oxygen.
at the ANODE, the negative electrode, hydrogen molecules are oxidised to H+ ions.
at the CATHODE, the positive electrode, oxygen molecules are reduced to O2- ions.
they then react to form water.
2H+ + o2- -> H20 (i think, someone please confirm)
advantages: water is renewable, only water is produced, so nonpollutant.
disadvantages: hydrogen is difficult to store and transport, is flammable.

remember, in an electrolysis, cathode is negative and anode is positive.
but in an electrochemical/fuel cell, anode is negative and cathode is positive.
the reasons for this switch are because oxidation ALWAYS takes place at anode and reduction ALWAYS takes place at cathode.
someone please confirm the final equation for me, hope this helped

No, the hydrogen molecules discharge at the Cathode- the negative electrode- since the H ions are positive. The oxygen discharges at the postive electrode- the anode. It's impossible to be the other way around. The chemical cell has no anodes and cathodes- the positive terminal is at the side of the more reactive metal.

 

[Micro961]

Is Naphta used for a fuel or just for heating systems? And which fraction exactly does it come out from? The book says nothing about it!

Naphtha* is used for making chemicals..
You first extract refinery gas then gasoline then Naphtha then paraffin etc..

 

[Penalopi]

Naphtha* is used for making chemicals..
You first extract refinery gas then gasoline then Naphtha then paraffin etc..

How many carbon atoms does a substance fractionating in the Naphtha column have?
e.g. From 1--> 5 carbon atoms fractionate as refinary gases

 

[Micro961]

How many carbon atoms does a substance fractionating in the Naphtha column have?
e.g. From 1--> 5 carbon atoms fractionate as refinary gases

You don't need to know that.. All you need to know is that from refinery gas to bitumen (last one), boiling point and length of carbon chain increases.

 

[Penalopi]

You don't need to know that.. All you need to know is that from refinery gas to bitumen (last one), boiling point and length of carbon chain increases.

oh, ok thanks :] good luck!