Biology; Chemistry; Physics: Post your doubts here!

[Vogue]

how r the percentiles counted. i mean is it centre wise, city wise or how?

 

[SalmanPakRocks]

 

[Vogue]

View attachment 9740

ok it says that 1 mole of Br gas reacts wid one mole of alkene.
luk at the choices. only A nd C are alkenes. thus B and D are cancelled
they hv given mass of bromine. so divide it by its molecular mass to get the # of moles. 16/160 = 0.1
so Bromine gas has 0.1 moles. now luk at the mass given for alkene which is 4.2
calculate the mass of alkene given in A which equals to 28
4.2/28 is NOT o.1
so this is cancelled
check the mass of option C which is 42
42/4.2 gives 0.1 moles
so thus u get ur answer which is C
ryt?

 

[ashiqbal]

The question said that there are granules IN the cells of the tuber. So, the "in" suggests we had to draw the inner part. plus, the label also indicated that!
but still, i'm not really sure whether i did the right thing.

no yaar, i think that the whole of the oval egg was to be drawn, as the picture mentioned that some granules were shown in the storage organ, and we had to draw one of the granule labelled Y. I dont think there was any mention of CELLS, though i could be wrong.

View attachment 9740

its (c) C3H6
the reason being the fact that
16 g of Br2 = 0.1 moles of Br2
0.1 mole of 4.2 g alkene, Mr of alkene = 42
only (a) and (c) are alkenes and only (c) has Mr 42, so there!

 

[asd]

ok it says that 1 mole of Br gas reacts wid one mole of alkene.
luk at the choices. only A nd C are alkenes. thus B and D are cancelled
they hv given mass of bromine. so divide it by its molecular mass to get the # of moles. 16/160 = 0.1
so Bromine gas has 0.1 moles. now luk at the mass given for alkene which is 4.2
calculate the mass of alkene given in A which equals to 28
4.2/28 is NOT o.1
so this is cancelled
check the mass of option C which is 42
42/4.2 gives 0.1 moles
so thus u get ur answer which is C
ryt?

Correct.

 

[Tharindu]

Is pottasium dichromate and permanganate used to test for oxidising agents or reducing???

 

[asd]

no yaar, i think that the whole of the oval egg was to be drawn, as the picture mentioned that some granules were shown in the storage organ, and we had to draw one of the granule labelled Y. I dont think there was any mention of CELLS, though i could be wrong.


I read the question very clearly dude, it said 'in the cells of tuber'. but I'm not still 100% sure that we had to draw the inner part.

 

[asd]

Is pottasium dichromate and permanganate used to test for oxidising agents or reducing???

These 2 are oxidising agents, so if they change colour it means they have been reduced. They test for reducing agents.

 

[Tharindu]

These 2 are oxidising agents, so if they change colour it means they have been reduced. They test for reducing agents.

They test for reducing agents....but they are oxidizing agents and they get reduced???? Does this make sense...pls help me

 

[SalmanPakRocks]

What if we don't practice graph questions from the ATP?
Because I don't have past papers available in printed form. Do I have to print them or it's ok to just leave making graph?

 

[asd]

They test for reducing agents....but they are oxidizing agents and they get reduced???? Does this make sense...pls help me

Listen, if something oxidizes anything, say giving away Oxygen atoms, it will be actually reducing itself. When it gives away O atoms, its reducing itself, so that the other thing can be oxidized.

 

[Tharindu]

Listen, if something oxidizes anything, say giving away Oxygen atoms, it will be actually reducing itself. When it gives away O atoms, its reducing itself, so that the other thing can be oxidized.

Ok thanks...finally get it

 

[luckywang]

They test for reducing agents....but they are oxidizing agents and they get reduced???? Does this make sense...pls help me

it make sense of coz! they are are oxidising mean they cause the other to be oxidise, when the other oxidised, the oxidising agent will also be reduced! am i right? so it is test for reducing agent! the reducing agent causes the oxidising agent to be reduced while the oxidising agent causes the reducing agent to be oxidised! correct me if im wrong!

 

[Tharindu]

it make sense of coz! they are are oxidising mean they cause the other to be oxidise, when the other oxidised, the oxidising agent will also be reduced! am i right? so it is test for reducing agent! the reducing agent causes the oxidising agent to be reduced while the oxidising agent causes the reducing agent to be oxidised! correct me if im wrong!

Ur right

 

[Tharindu]

it make sense of coz! they are are oxidising mean they cause the other to be oxidise, when the other oxidised, the oxidising agent will also be reduced! am i right? so it is test for reducing agent! the reducing agent causes the oxidising agent to be reduced while the oxidising agent causes the reducing agent to be oxidised! correct me if im wrong!

So does the color change occur when oxidizing takes place or resuction....according to yours both has happened...I'm sorry I'm not that good at chemistry, pls help if I'm wrong

 

[ashiqbal]

I read the question very clearly dude, it said 'in the cells of tuber'. but I'm not still 100% sure that we had to draw the inner part.

but actually, the labelling line of "Y" did not extend to the inner small circle.
anyway, it was of two marks only!

 

[luckywang]

help me in the chemistry syllabus please....

-describe methods of purification of liquid air and fermented liquor.
-describe and explain evidence for the movement of particles in liquids and gases
-state that some isotopes are radioactive. example?
-how can photosynthesis provide a renewable energy source?
-describe the general rules of solubility?
-what are soluble and insoluble in hydroxide, group 1 and ammonium salts?
-state the uses of oxygen?
-the use of calcium carbonate to reduce the effect of 'acid rain' and in flue gas desulfurisation?
- the effect of acid rain in respiration? and is acid rain promotes plant growth?
- how to deduce the structure of polymer product from a given monomer?
-describe protein&fats as possessing the same amide/ester linkage as nylon/terylene but with different monomer unit?
-describe the hydrolysis of proteins to amino acids and carbohydrates to simple sugar? same as the one in biology?

 

[ashiqbal]

So does the color change occur when oxidizing takes place or resuction....according to yours both has happened...I'm sorry I'm not that good at chemistry, pls help if I'm wrong

the colour changes from "orange to green" and "purple to colourless" when "potassium dichromate" and "potassium mangnate" are added to a reducing agent respectively!(they are oxidising agents)
and the colour changes from colourless to brown when potassium iodide is added to any oxidising agent(it is a reducing agent)

 

[luckywang]

So does the color change occur when oxidizing takes place or resuction....according to yours both has happened...I'm sorry I'm not that good at chemistry, pls help if I'm wrong

according to the reaction?

 

[asd]

but actually, the labelling line of "Y" did not extend to the inner small circle.
anyway, it was of two marks only!

Yeah, actually the marks made me make the inner oval, at first i drew the whole thing!