CHEM AND BIO HELP AND TIPS HERE

[rameeziiii]

the functional group is -COOH.... sometimes written as -CO₂H... and how would that work? C_nH_2nO₂? that would remove one the hydrogens...

[basharooo]

i have a quick question the formula for acids is cnh2n+1 cooh but i read that there is a new formula which works the same cnh2n o2 how can it be the same

the correct forumla of acid is Cn-1 H2n-1COOH

[basharooo]

I have an important question and it is expected to come in the chemistry paper 3

-describe the use of hydrogen as a potential fuel reacting with oxygen to generate electricity in a fuel cell ??

is this is new ,, i never saw a quetion in the past papers about this topic, if there is any quetion in the pastpapers plz post it here !!

[Ivo]

the correct forumla of acid is Cn-1 H2n-1COOH

I don't think there's a -1.  I think this is it:

C_nH_2n+1COOH

[nid404]

I don't think there's a -1.  I think this is it:

C_nH_2n+1COOH

yup that's right.

[Ivo]

I have an important question and it is expected to come in the chemistry paper 3

-describe the use of hydrogen as a potential fuel reacting with oxygen to generate electricity in a fuel cell ??

is this is new ,, i never saw a quetion in the past papers about this topic, if there is any quetion in the pastpapers plz post it here !!

There would not be any past paper questions for this particular topic as it is new for the 2010 syllabus (any new material for the 2010 syllabus is highlighted by black veritcal lines either side of the text.

[nid404]

I have an important question and it is expected to come in the chemistry paper 3

-describe the use of hydrogen as a potential fuel reacting with oxygen to generate electricity in a fuel cell ??

is this is new ,, i never saw a quetion in the past papers about this topic, if there is any quetion in the pastpapers plz post it here !!

It's a potential fuel cause it is non-polluting. The products of the reaction in the cell is water. It also has a high efficiency and requires less maintenance.  

[Ivo]

There would not be any past paper questions for this particular topic as it is new for the 2010 syllabus (any new material for the 2010 syllabus is highlighted by black veritcal lines either side of the text.

Because the syllabus also says:

details of the construction and operation of a fuel cell are not required

I guess the key points you would need to know is:

1) A hydrogen-oxygen fuel cell produces only water as a product.

2) A hydrogen-oxygen fuel cell is efficient and non-polluting.

3) When a fuel cell is working, hydrogen loses electrons at the cathode and oxygen gains electrons at the anode.

Here's a nice diagram!  

[J.Darren]

There would not be any past paper questions for this particular topic as it is new for the 2010 syllabus (any new material for the 2010 syllabus is highlighted by black veritcal lines either side of the text.

... The IGCSE Chemistry Revision Guide, which was published in 2006 / 2007, has devoted a page to hydrogen fuel cells

Would it be considered as copyright infringement if I were to scan and upload that particular page ?

[holtadit]

... The IGCSE Chemistry Revision Guide, which was published in 2006 / 2007, has devoted a page to hydrogen fuel cells

Would it be considered as copyright infringement if I were to scan and upload that particular page ?

Nope

[J.Darren]

Nope

Hydrogen fuel cells

Advantages :

- Most energy rich (releases more energy per kg than any other conventional fuel)
- Only product of combustion is water
- Oxides of nitrogen are not produced

Disadvantages :

- Difficult to store
- Expensive to produce

H2 -> 2H+ + 2e-

O2 + 2H2O + 4e- -> 4OH-

H+ + OH- -> H2O

2H2 + O2 > 2H2O

[sarasa]

Because the syllabus also says:
I guess the key points you would need to know is:

1) A hydrogen-oxygen fuel cell produces only water as a product.

2) A hydrogen-oxygen fuel cell is efficient and non-polluting.

3) When a fuel cell is working, hydrogen loses electrons at the cathode and oxygen gains electrons at the anode.

Here's a nice diagram!  

I believe u have reversed them, hydrogen at the anode nd oxygen at da cathode.
This is opposite of electrolysis. It's shown by ur diagram even...!

[Ivo]

I believe u have reversed them, hydrogen at the anode nd oxygen at da cathode.
This is opposite of electrolysis. It's shown by ur diagram even...!

Hmm, I'm pretty sure reaction invovling hydrogen happens at cathode and likewise for oxygen at the anode.  I guess the diagram I chose was a bit weird, because if you look carefully, there are the - sign in hydrogen and + in oxygen.

My 'case' for this is also exemplified by this link:

http://inventors.about.com/od/sstartinventions/ss/Physics_Illustr_2.htm

[Raywin]

I believe u have reversed them, hydrogen at the anode nd oxygen at da cathode.
This is opposite of electrolysis. It's shown by ur diagram even...!

See this diagram. I found it pretty good.

[Vin]

Guys a stupid doubt ... How to name this? I seriously forgot