Biology; Chemistry; Physics: Post your doubts here!

[Alpha Destro]

Chemistry is a piece of cake all advice that i can give is ;
1) be very careful to include state symbols when writing chemical equations especially when stated so in the question.
2) When drawing dot and cross diagrams of atoms remember to put the ions in brackets and write the charge on them i.e [ structure of ion ] charge+-
and remember to show clearly electron belonging to there respective atoms.(don't mix them up )
3)when taking about why a substance conducts electricity mention free or delocalized electrons.
4) HCL IS A COVALENT COMPOUND don't forget it ( i always forget it).
5) always convert cm3 into dm3 when calculating concentration or volume.
6) in electrolysis the +electrode is the anode and the -electrode is the cathode but in the case of a simple cell its the other way around.
7) during electrolysis of CuSO4 with inert electrodes the color of the solution fades.
Other than this there isn't anything i need to be reminded of before the paper .

For physic i have to do lots , so i don't have any good advice but if there is a problem to be solved i would be glad to help.

 

[Qasim Hafeez]

Chemistry is a piece of cake all advice that i can give is ;
1) be very careful to include state symbols when writing chemical equations especially when stated so in the question.
2) When drawing dot and cross diagrams of atoms remember to put the ions in brackets and write the charge on them i.e [ structure of ion ] charge+-
and remember to show clearly electron belonging to there respective atoms.(don't mix them up )
3)when taking about why a substance conducts electricity mention free or delocalized electrons.
4) HCL IS A COVALENT COMPOUND don't forget it ( i always forget it).
5) always convert cm3 into dm3 when calculating concentration or volume.
6) in electrolysis the +electrode is the anode and the -electrode is the cathode but in the case of a simple cell its the other way around.
7) during electrolysis of CuSO4 with copper electrodes the color of the solution fades.
Other than this there isn't anything i need to be reminded of before the paper .

For physic i have to do lots , so i don't have any good advice but if there is a problem to be solved i would be glad to help.

Thanks and anything for p4?

 

[Alpha Destro]

Be damn careful in the titration question, the one they give evey time.Remember to read it really really carefully because that's where they want to trick you and that's where you get swindled mostly. the fifth advice comes in real handy here . there are also lots of calculation so remember to check twice and if you get weird answers check thrice.
Even the best candidates lose marks here because of silly mistakes.

 

[Dark Destination]

https://www.xtremepapers.com/community/threads/full-o-level-guidance-and-help.37126/

Help provided here ^

 

[tayyab9801]

Can anyone solve this mole question?

 

[Alpha Destro]

Can anyone solve this mole question?

it might just be correct ,i hope its

 

[Cornflakes112]

Chemistry is a piece of cake all advice that i can give is ;
1) be very careful to include state symbols when writing chemical equations especially when stated so in the question.
2) When drawing dot and cross diagrams of atoms remember to put the ions in brackets and write the charge on them i.e [ structure of ion ] charge+-
and remember to show clearly electron belonging to there respective atoms.(don't mix them up )
3)when taking about why a substance conducts electricity mention free or delocalized electrons.
4) HCL IS A COVALENT COMPOUND don't forget it ( i always forget it).
5) always convert cm3 into dm3 when calculating concentration or volume.
6) in electrolysis the +electrode is the anode and the -electrode is the cathode but in the case of a simple cell its the other way around.
7) during electrolysis of CuSO4 with copper electrodes the color of the solution fades.
Other than this there isn't anything i need to be reminded of before the paper .

For physic i have to do lots , so i don't have any good advice but if there is a problem to be solved i would be glad to help.

"during electrolysis of CuSO4 with copper electrodes the color of the solution fades" it does not according to my book(complete chemistry) http://www.docbrown.info/page01/ExIndChem/electrochemistry04.htm

 

[tayyab9801]

it might just be correct ,i hope its

I did the same but the marking scheme says something else:

 

[Alpha Destro]

"during electrolysis of CuSO4 with copper electrodes the color of the solution fades" it does not according to my book(complete chemistry) http://www.docbrown.info/page01/ExIndChem/electrochemistry04.htm

WHAT? u use complete chemistry? it is the worst book for chemistry lots of stuff is missing , i would advise u to burn it get matters of the green Federal one
By the way it does fade with inert electrodes because i have read it in a mark scheme and i am pretty sure the same thing happens with copper electrodes.

 

[Dark Destination]

WHAT? u use complete chemistry? it is the worst book for chemistry lots of stuff is missing , i would advise u to burn it get matters of the green Federal one
By the way it does fade with inert electrodes because i have read it in a mark scheme and i am pretty sure the same thing happens with copper electrodes.

Not with Copper electrodes.
It fades if you use Graphite (Inert) electrodes, due to the continuous discharge of Copper ions on the Cathode the concentration of Copper ions decreases and ultimately becomes zero.
So no copper ions in solution = No blue color. So the color fades with GRAPHITE electrodes.

However, with copper electrodes, the color does not fade.
For every copper ion that discharges on Cathode, one new copper ion comes into the solution from the positively charged Copper anode:

Cu --> Cu+2 + 2e

So the net concentration of Copper remains almost constant and does not change much. So the color of the solution does not fade!

 

[Alpha Destro]

1 tonne of Mo is not = to 10417 moles hows that possible? we are suppose to divide mass by Mr to get no.moles but this ans is totally different I am 100% confirmed that i did it right but something is fishy here we need an expert on the case any recommendations?

 

[Dark Destination]

1 tonne of Mo is not = to 10417 moles hows that possible? we are suppose to divide mass by Mr to get no.moles but this ans is totally different I am 100% confirmed that i did it right but something is fishy here we need an expert on the case any recommendations?

You are wrong. You are using atomic number instead of Atomic Mass.

The marking scheme is totally right. Calculate the answer again, using the correct Ar that is 96!

42 is the Atomic NUMBER, as the question says.

 

[Alpha Destro]

So right dude i hate it when i make mistakes like these lesson well learned

 

[Dark Destination]

So right dude i hate it when i make mistakes like these lesson well learned

If it's any consolation, even i misread it at first. Even though i aced O-Level Chemistry last year.
I used 42 blindly. xD

Idk why we ALL misread it. Something about this question is really twisted! o_o'

 

[Cornflakes112]

WHAT? u use complete chemistry? it is the worst book for chemistry lots of stuff is missing , i would advise u to burn it get matters of the green Federal one
By the way it does fade with inert electrodes because i have read it in a mark scheme and i am pretty sure the same thing happens with copper electrodes.

The problem is, complete chemistry contains a few details that are not in Presscott.I use both of them.

 

[tayyab9801]

You are wrong. You are using atomic number instead of Atomic Mass.

The marking scheme is totally right. Calculate the answer again, using the correct Ar that is 96!

42 is the Atomic NUMBER, as the question says.

Wooff!!! Such a careless mistake.

 

[Dark Destination]

Wooff!!! Such a careless mistake.

Woof? What are you, a dog?

 

[Alpha Destro]

Woof? What are you, a dog?

i think he meant oof as in enough , right?

 

[Qasim Hafeez]

Guys can anyone tell me what are the topics that are likely to come in Physics ATP? And also please tell which topics are likely or mostly come in P2 of chemistry! I need help badly pls

 

[tayyab9801]

Woof? What are you, a dog?