Biology; Chemistry; Physics: Post your doubts here!

[asadalam]

SO i should go for each and every topic eh
Okay
Thanks for the help
have you got any good notes on this section?

 

[Maganius]

Thanks

 

[***amd***]

if we induce a magnetism in a simple i rod this way i.e. not making them touch each other. will the iron rod still posssess magnetism even after the magnet is taken away?

 

[Dark Destination]

View attachment 36635
if we induce a magnetism in a simple i rod this way i.e. not making them touch each other. will the iron rod still posssess magnetism even after the magnet is taken away?

I don't think so. ._.
Iron gets easily magnetized and easily demagnetized, right?
So when we move the magnet away, the magnetic domains in the iron rod will get dis-aligned, and the induced magnetism will go away.

 

[***amd***]

Physicists believe that the orbiting motion of electrons in a magnetic material makes each atom an atomic magnet.A group of such atomic magnets pointing in the same direction is called a magnetic domain.

can somebody tell me what does this "pointing in same direction" mean?

 

[Awesome12]

can somebody tell me what does this "pointing in same direction" mean?

i think it means the same direction of motion of electrons in the simplest way

 

[Awesome12]

View attachment 36635
if we induce a magnetism in a simple i rod this way i.e. not making them touch each other. will the iron rod still posssess magnetism even after the magnet is taken away?

now iron is a soft magnetic material which easily magnetizes and demagnetizes and the magnet is only temporary. Hence they are also called permanent magnetic material
magnetism will quickly be induced in the magnet, but when we move the magnet away, it will quickly demagnetize

if we had a steel rod, then magnetism induced wud not be that strong (which is y we use a solenoid to magnetize it), but it wud be permanent

 

[Izhaan]

Ahhh. Can someone tell me how to prepare for atp's? I mean should i just go thro past papers & nothing else or just rely on my knowledge

 

[***amd***]

Ahhh. Can someone tell me how to prepare for atp's? I mean should i just go thro past papers & nothing else or just rely on my knowledge

go through past papers

 

[Awesome12]

Ahhh. Can someone tell me how to prepare for atp's? I mean should i just go thro past papers & nothing else or just rely on my knowledge

atp is the easiest part of the paper
first of all u need to have good knowledge of the entire syllabus. after that solve as many past papers and note down the common questions and their answers. like this the atp will become even more easier to ace

 

[Awesome12]

could someone plz help me here

https://www.xtremepapers.com/community/threads/best-old-past-paper-books-for-o-levels.31903/

 

[Dream.Eater]

Hi.
I've come across a bit of a tricky question in the Oct/Nov 2013 chemistry paper 21.
Its question B9 part b. Here's the question
''The reaction between ethanoic acid and sodium hydroxide is described as a neutralisation reaction. Write the simplest ionic equation for this reaction''
Now, it is known that the simplest ionic eq is H+ + OH- = H2O in this base of acid-base neutralisation. But since ethanoic is a weak acid undergoing partial dissociation into H+ ions the ionic eq should be
CH3COOH + OH- = CH3COO- + H+
Im confused as to which eq is correct. Could someone please clarify this ?
Thanks in advance !!
Btw-ive attached a screenshot of the question.

 

[Awesome12]

Hi.
I've come across a bit of a tricky question in the Oct/Nov 2013 chemistry paper 21.
Its question B9 part b. Here's the question
''The reaction between ethanoic acid and sodium hydroxide is described as a neutralisation reaction. Write the simplest ionic equation for this reaction''
Now, it is known that the simplest ionic eq is H+ + OH- = H2O in this base of acid-base neutralisation. But since ethanoic is a weak acid undergoing partial dissociation into H+ ions the ionic eq should be
CH3COOH + OH- = CH3COO- + H+
Im confused as to which eq is correct. Could someone please clarify this ?
Thanks in advance !!
Btw-ive attached a screenshot of the question.

yes u do have a point
however the ionic equation will still be
CH3COOH + NaOH ----> CH3COONa + H2O
CH3COO -1 + H+1 + Na +1 + OH-1 ----> CH3COO-1 + Na+1 + H2O

CH3COO-1, and Na+1 will be eliminated
thus the equation will be

H+1 + OH-1 ----> H2O

 

[Awesome12]

and yes u shud stick to the CIE one. in the marking scheme, the answer is the same as my last equation.
so yes u shud reserve that answer to the neutralization questions

 

[asadalam]

and yes u shud stick to the CIE one. in the marking scheme, the answer is the same as my last equation.
so yes u shud reserve that answer to the neutralization questions

Here you can see the exact same question(NaOH with C2H5COOH) but the ionic equation in the ms is given with the ethanoate ion instead of the hydroxide ion.I'm a bit confused to what to do in case we face this question in our exam.

 

[Awesome12]

Here you can see the exact same question(NaOH with C2H5COOH) but the ionic equation in the ms is given with the ethanoate ion instead of the hydroxide ion.I'm a bit confused to what to do in case we face this question in our exam.

there is no need to worry

here is a snapshot from the examiner report

 

[asadalam]

there is no need to worry

here is a snapshot from the examiner report

View attachment 36813

Thanks a lot!I was unable to find the er so i was unsure

 

[Awesome12]

Thanks a lot!I was unable to find the er so i was unsure

np

 

[Dream.Eater]

there is no need to worry

here is a snapshot from the examiner report

View attachment 36813

Thanks a lot!
I guess its best to stick to the usual ionic eq regardless of whether the acid is weak
or not

 

[Dream.Eater]

Hi,
I'm stuck in an mcq in the may June 2007 chem paper 1
Its Q33 about eutrophication.
Can anyone tell me why the ans is C instead of A ?
Thanks!