Biology; Chemistry; Physics: Post your doubts here!

[Awesome12]

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!

excellent question
well the answer is C because
B and D are not possible because O2 depletion is caused instead of O2 excess
that leaves us with A and C
nitrates are not found in detergents
instead phosphates are, and thus the answer is
C

 

[asadalam]

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!

Detergents dont contain nitrates,although they contain Phosphates,which are another important fertilizer ion.Hence they cause excessive plant growth and you know the rest

 

[asadalam]

Can someone explain these to me?

 

[Dream.Eater]

excellent question
well the answer is C because
B and D are not possible because O2 depletion is caused instead of O2 excess
that leaves us with A and C
nitrates are not found in detergents
instead phosphates are, and thus the answer is
C

Thanks a lot

 

[Dream.Eater]

View attachment 36978 View attachment 36976

Can someone explain these to me?

Ans to Q15 is D. This is because only copper and silver ions get reduced and also silver is heavier than copper so D is the answer. Pb and Al do not get reduced since they're more reactive than hydrogen.

Ans to Q11 is A. The balanced eq is 2C4H10 + 13O2 =8CO2 + 10H2O
and since its given that all volumes are measured at RTP the volume ratio is equal to the reacting molar ratio(stoichiometry). So u have to find out which alkane reaches completely in a 2:13 ratio and the only one here is butane so A is the ans. Try working out the complete eq from scratch and you'll understand it 100%
Hope this helps!

 

[Awesome12]

Thanks a lot

np

 

[asadalam]

Ans to Q15 is D. This is because only copper and silver ions get reduced and also silver is heavier than copper so D is the answer. Pb and Al do not get reduced since they're more reactive than hydrogen.

Ans to Q11 is A. The balanced eq is 2C4H10 + 13O2 =8CO2 + 10H2O
and since its given that all volumes are measured at RTP the volume ratio is equal to the reacting molar ratio(stoichiometry). So u have to find out which alkane reaches completely in a 2:13 ratio and the only one here is butane so A is the ans. Try working out the complete eq from scratch and you'll understand it 100%
Hope this helps!

Thanks a lot bro!

 

[Dream.Eater]

Thanks a lot bro!

Always happy to help!

 

[Abdul96]

From where can we download the REVISION CHECKLIST of Chemistry and Physics???

 

[Awesome12]

From where can we download the REVISION CHECKLIST of Chemistry and Physics???

u can google it

 

[Dream.Eater]

I've stumbled across 2 difficult mcqs in the 2012 Oct physics paper 12. Could someone please explain these two?Thanks!

 

[Awesome12]

I've stumbled across 2 difficult mcqs in the 2012 Oct physics paper 12. Could someone please explain these two?Thanks!View attachment 37088View attachment 37089

for the first one (question no. 4),
the statement in the question is tricky. Candidates will go on without actually attentively reading the question, applying their old techinque of finding the gradient, but fail to comply with the question. the question states
'What is the acceleration of the car at 30s'
normally acceleration is always asked between a set of values, like between 20 and 30s.
However over here the acceleration at a particular point is asked, which is 0

For the second question, again in the question lies the solution to the trick
the question states, ' The reflected wavefronts are also parts of circles'
since the image of an object is always at an equal distance from the mirror as the distance of the object from the mirror, the centre of the wavefronts will be at the same place as the vibrator, only behind the flat surface.
Thus the answer is A


For the second question

 

[Dream.Eater]

for the first one (question no. 4),
the statement in the question is tricky. Candidates will go on without actually attentively reading the question, applying their old techinque of finding the gradient, but fail to comply with the question. the question states
'What is the acceleration of the car at 30s'
normally acceleration is always asked between a set of values, like between 20 and 30s.
However over here the acceleration at a particular point is asked, which is 0

For the second question, again in the question lies the solution to the trick
the question states, ' The reflected wavefronts are also parts of circles'
since the image of an object is always at an equal distance from the mirror as the distance of the object from the mirror, the centre of the wavefronts will be at the same place as the vibrator, only behind the flat surface.
Thus the answer is A

For the second question

Thanks a lot!

 

[kirann]

Problem in answering atp questions of bio and chem. Any resources?

 

[Dark Destination]

How long will it take to do the past papers of Physics, Chem, Bio..?

 

[asadalam]

How long will it take to do the past papers of Physics, Chem, Bio..?

How long will it take to do the past papers of Physics, Chem, Bio..?

TBH it took me around a month and a half,including maths paper.I did 4 P2 and 8P1 a day alternatively.

 

[Dark Destination]

TBH it took me around a month and a half,including maths paper.I did 4 P2 and 8P1 a day alternatively.

But those 4 p2's, and p1's.. were of the same subject?
Or did you do different subjects each day?

 

[kirann]

Any resources for chem and bio atp? plZ anyone?

 

[asadalam]

But those 4 p2's, and p1's.. were of the same subject?
Or did you do different subjects each day?

Same subject for one day

 

[Awesome12]

Could someone give me the ideal curve for the last part?
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_qp_42.pdf
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Physics (5054)/5054_s11_ms_42.pdf
It's kind of urgent.