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Biology; Chemistry; Physics: Post your doubts here!

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Anees2rehman

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Khadija_1234 said:
http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_w09_qp_6.pdf
Help needed, Q3 (b)
Click to expand...

Bean seeds of different sizes are planted. The germination should take place at a constant conditions e.g temperature. When new seeds are
Formed they are measured and a table of results is made. Now we repeat the experiment by plNting these seeds at diff conditions e.g
Temperature. The new seeds formed r measured. They show almost the same variation in results as the first exp, I.e small and large seeds
Mixed. Therefore short seeds don't depend on environmental conditions. Hope it helps:)
 
ijlalm

ijlalm

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passion hunter said:
i know what you are trying to say but perpendicular distance will not matter unless there is equal force on both sides.....
Click to expand...
you can see in the diagram that the rod is balanced..now the force of the screw remains constant, but the perp. distance decreases when we make the screw go in .As moment=f x d the moment decreased..and the left side goes up. nothing is changed on the right side it goes down..
 
sourov97

sourov97

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can anyone please explain me the transmission of pressure in hydraulic systems; ...hydraulic press, hydraulic brakes on vehicles......as written in the physics syllabus - 5054_y13_sy....content 7...learnig outcome (g)..
 
K

Khadija_1234

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Exp: to find out whether CO2 is given off during fermentation

Testube with a rubber bung on top containing distiller water is connected to a testtube containg lime water by a delivery tube.
1.Add few grains of dry yeast in destilled water in a boiling tube.
2.After 20 mins add an equal anoint og dilute glucose solution and mix well. Add a little oil.

What does the layer of oil serve as?

What do you observe after some time?

What would you add to the boiling water in the control?
 
Iridescent

Iridescent

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Khadija_1234 said:
Exp: to find out whether CO2 is given off during fermentation

Testube with a rubber bung on top containing distiller water is connected to a testtube containg lime water by a delivery tube.
1.Add few grains of dry yeast in destilled water in a boiling tube.
2.After 20 mins add an equal anoint og dilute glucose solution and mix well. Add a little oil.

What does the layer of oil serve as?

What do you observe after some time?

What would you add to the boiling water in the control?
Click to expand...
The layer of oil will prevent oxygen from coming in contact with the yeast so that inaerobic respiration could occur.

The lime water will turn milky due to the CO2 produced.

You will conduct the same experiment with the boiling water. The only difference must be the temp. of water. The boiling water will kill the yeast so no CO2 will be produced and the lime water does not turn milky. It is to prove that CO2 was produced due to the some metabolic reactions taking place in the yeast.
 
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danishnxt

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Hi everyone, I'd really appreciate it if someone could help me grasp the concept behind Q9 D in this paper (Given Below). Chemistry ATP Year 2006 May June.

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s06_qp_4.pdf

Question tells us that Iron (II) Sulfate and Iron (III) Sulphate are in a solution. First off Iron 3 sulfate is Red right? Secondly they say that they add H2SO4 To it. What effect are they causing with that. As afterwards adding KMnO4 oxidises the GREEN FE(II) and discolours the oxidation agent as well, then apparently the colour in the flask changes to Pink. My question is what happened to the RED coloured FE(III) Ions? They are still in the solvent but why does their colour not have an affect, I could be very mistaken with the fact that the colour is somehow related to the Reaction with H2So4 but this is the only question that has been really bugging me for a while now.

Would really appreciate if someone could help me out with this.
 
H

hmrflower

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guys biology p6 in general do we have to study inheritance questions?? cuz i never found an inheritance question p6?
 
sourov97

sourov97

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danishnxt said:
Hi everyone, I'd really appreciate it if someone could help me grasp the concept behind Q9 D in this paper (Given Below). Chemistry ATP Year 2006 May June.

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Chemistry (5070)/5070_s06_qp_4.pdf

Question tells us that Iron (II) Sulfate and Iron (III) Sulphate are in a solution. First off Iron 3 sulfate is Red right? Secondly they say that they add H2SO4 To it. What effect are they causing with that. As afterwards adding KMnO4 oxidises the GREEN FE(II) and discolours the oxidation agent as well, then apparently the colour in the flask changes to Pink. My question is what happened to the RED coloured FE(III) Ions? They are still in the solvent but why does their colour not have an affect, I could be very mistaken with the fact that the colour is somehow related to the Reaction with H2So4 but this is the only question that has been really bugging me for a while now.

Would really appreciate if someone could help me out with this.
Click to expand...
Firstly, Iron(III) Sulphate (aq) is somewhat a red-brown solution.
Secondly, here H2SO4 is added as a reagent for titration, o level syllabus includes only acid-basic titration and redox titration (this one)
but where did u get: oxidation agent is decolourised?
KMnO4 has no effect on Fe3+... this is because Fe3+ is already in its highest oxidation state and cannot be further oxidised to Fe4+....hence, its unreactive enen though its present in the mixture.
i, too, was confused with the addition of H2SO4... i just got these suggetions from my chemistry teachers....
hope it helps. :)
 
D

danishnxt

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sourov97 said:
Firstly, Iron(III) Sulphate (aq) is somewhat a red-brown solution.
Secondly, here H2SO4 is added as a reagent for titration, o level syllabus includes only acid-basic titration and redox titration (this one)
but where did u get: oxidation agent is decolourised?
KMnO4 has no effect on Fe3+... this is because Fe3+ is already in its highest oxidation state and cannot be further oxidised to Fe4+....hence, its unreactive even though its present in the mixture.
i, too, was confused with the addition of H2SO4... i just got these suggestions from my chemistry teachers....
hope it helps. :)
Click to expand...


Thanks a lot! The oxidation reagent as in KMnO4 gets decolourised when it gets reduced I believe from purple to colourless. I see. Ok but just one more thing If I could trouble you once more. Iron 3 is reddish brown as you correctly pointed out, so after the H2SO4 is added the Solution turns Green thanks to the Iron 2 which then later gets decolourised, but the thing is the Reddish brown Iron 3 ions are also still present in the mixture, won't its colour affect the solutions colour? Also, when the Iron 2 is oxidised to Iron 3. Those Ions won't have a reddish brown colour?

Thanks in Advance

Danish
 
simranlalchand

simranlalchand

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if we have readings that begin from ph3 so can we draw a graph begining from ph3 rather than starting from ph 1
 
sourov97

sourov97

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danishnxt said:
Thanks a lot! The oxidation reagent as in KMnO4 gets decolourised when it gets reduced I believe from purple to colourless. I see. Ok but just one more thing If I could trouble you once more. Iron 3 is reddish brown as you correctly pointed out, so after the H2SO4 is added the Solution turns Green thanks to the Iron 2 which then later gets decolourised, but the thing is the Reddish brown Iron 3 ions are also still present in the mixture, won't its colour affect the solutions colour? Also, when the Iron 2 is oxidised to Iron 3. Those Ions won't have a reddish brown colour?

Thanks in Advance

Danish
Click to expand...
thanks for bugging again...I was chatting with my teacher whom i mentioned earlier and gushed your problems to him...your questions has left me confused as well...
i mentioned the colour of Fe3+ as according to the test of ions..for ex- BaSO4 is white (ppt of sulphate), AgI is yellow etc...
u should see that the solutions had been diluted with acid (100 cm3) and then with water (250 cm3) both of which are colourless.... hence, even if a colour of Fe(II)/Fe(III) sulphate had existed, it should fade and the solution should turn colourless.
i am still confused with why the green colour has been accepted, but shouldn't cause prob as colourless is also correct..u can go with it too.
hope it helps :)
 
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