Biology; Chemistry; Physics: Post your doubts here!

[asadalam]

Not wearing Black Trouser OR Red Shirt.

They mentioned OR. Which means we have to eliminate the options in which he wears either a black trouser or a red shirt i.e that in which he wears a black trouser and a yellow shirt, and the one in which he wears a grey trouser and red shirt. The Black and Red can't be together as they mentioned in the question ''OR''. ._.

If they had said ''the probability of wearing NEITHER a Black trouser NOR a red shirt''.. then the logical option would be Grey Trouser and Yellow Shirt, since both Black AND Red are not to be included.
But they mentioned in the question ''EITHER and OR''..
Either means ONE OF THE TWO.

So the probability of wearing EITHER BLACK or RED SHIRT.. (Can't be both, since they used the words ''Either'' and ''Or'')

The following: BY, GR.. (Not BR, since they didn't say Black AND RED)

And the question said ''Probability of NOT wearing Either black or red''..
So, 1 - (probability of BY, GR)...

This should be right :/

It really depends on how you view the question,but i guess its a pretty vague question.Either way,i just showed you the correct way the came into my mind,which turned out to be right.

 

[funky brat]

Which year?

Can I get the 90's papers?

 

[Nabeel.Ahmad]

Can I get the 90's papers?

Yes. But not on the internet, i guess.
Old Redspots..

 

[funky brat]

Yes. But not on the internet, i guess.
Old Redspots..

Actually I don't want the redspot thing.

 

[Nabeel.Ahmad]

Actually I don't want the redspot thing.

Well, actual papers are not available before 2002 on the internet.
In order to get the past questions before 2002, that is the only resource.

Why?

 

[scouserlfc]

Well, actual papers are not available before 2002 on the internet.
In order to get the past questions before 2002, that is the only resource.

Why?

Actually I don't want the redspot thing.

You can always get Classified papers for before 90s questions. they also have answers for MCQs and also some answers for the theory part of the papers like calculation answers not bad but u wont get all answers there thats the only drawback

 

[black widow]

May-June 2011 paper 11. Question 21, part c.

in order to increase the pH of acidic oxides, we will need a basic oxide (base)
bases are a group of chemical elements consisting of all metal oxides and metal hydroxides
CaCO3 will decompose to CaO, CO2. the CO2 will go in to the air, leaving behind the base (CaO)

 

[funky brat]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s07_qp_1.pdf
Anyone please help me with the 11th MCQ. I know the answer is D, the root hair has a large surface area but isn't the ion uptake through active transport which is option A?

 

[black widow]

http://papers.xtremepapers.com/CIE/Cambridge International O Level/Biology (5090)/5090_s07_qp_1.pdf
Anyone please help me with the 11th MCQ. I know the answer is D, the root hair has a large surface area but isn't the ion uptake through active transport which is option A?

the question says that the root hair cell is absorbing ions (ie. active transport). if there is a higher conc. of ions in the soil than in the cell sap then diffusion of ions will occur rather than active transport. a large surface areas increases surface area to vol. ratio which means that a greater no. of ions can be absorbed in a unit time

 

[black widow]

cud someone plz explain question 8 (b) i just dont get the colour change

 

[scouserlfc]

cud someone plz explain question 8 (b) i just dont get the colour change

Have you read it properly if it still baffles you make a diagram of it. heres how that happens. You have Fe2+ salt in the flask and that contains acid with it this is called G and then you have KMnO4 coming from burette into the flask this solution is called F.
So the colour before F is added needs to be iron2+ salt colour which may be called green or colourless. Its better to call it green as iron 2+ salts are mostly green but ms also allows colourless ! Now at end point this is the important bit, KMnO4 is purple/pink whatever u wish . As you add a drop of F which is pink and goes in solution it becomes colourless so lets assume you go on adding and u reach a time when the drops added no more go colourless instead they now turn thr solution pink. What does this mean it means that KMnO4 is slightly in excess and all Fe2+ has been reacted with. So if u do the titration you have an idea that as soon as colour changes i need to stop and thats the amount required to react with Fe2+

 

[black widow]

Have you read it properly if it still baffles you make a diagram of it. heres how that happens. You have Fe2+ salt in the flask and that contains acid with it this is called G and then you have KMnO4 coming from burette into the flask this solution is called F.
So the colour before F is added needs to be iron2+ salt colour which may be called green or colourless. Its better to call it green as iron 2+ salts are mostly green but ms also allows colourless ! Now at end point this is the important bit, KMnO4 is purple/pink whatever u wish . As you add a drop of F which is pink and goes in solution it becomes colourless so lets assume you go on adding and u reach a time when the drops added no more go colourless instead they now turn thr solution pink. What does this mean it means that KMnO4 is slightly in excess and all Fe2+ has been reacted with. So if u do the titration you have an idea that as soon as colour changes i need to stop and thats the amount required to react with Fe2+

thnx for the explanation

 

[scouserlfc]

thnx for the explanation

Welcome

 

[Faizan Muhammmad]

Circuit as shown in figure

Switch closed what happens?
Since capacitor is charging for some time all current falls on it but in the end does the bulb light up?
And does it light up continuosly or the capacitor discharges in process and hence the bulb blinks ?

Thanks in advance

 

[Nabeel.Ahmad]

Is it a good idea to do unsolved past papers, of Physics Chemistry and Biology?
Or should i stick to the Topical?

 

[black widow]

Is it a good idea to do unsolved past papers, of Physics Chemistry and Biology?
Or should i stick to the Topical?

u shud do both
while studying the sub do topical
when u have completely a sub do unsolved past papers
btw. avoid redspot answers and try ur best to write ur answers based on the marking scheme. redspot contains irrelevant, vague, and false answers
so like i said stick to the marking scheme

 

[funky brat]

Is it a good idea to do unsolved past papers, of Physics Chemistry and Biology?
Or should i stick to the Topical?

No, don't stick to the topicals. They are just for your understanding. Do them when you read a topic to check that you have a grip on that particular topic from examination's point of view. Unsolved papers are the best and consult the MS, of course.

 

[Nabeel.Ahmad]

No, don't stick to the topicals. They are just for your understanding. Do them when you read a topic to check that you have a grip on that particular topic from examination's point of view. Unsolved papers are the best and consult the MS, of course.

But there are not any explanations for answers in Marking Schemes. :/
Like for MCQs.

What about Examiner Reports?

 

[funky brat]

But there are not any explanations for answers in Marking Schemes. :/
Like for MCQs.

What about Examiner Reports?

Yeah, that's the problem. But again, redpsot does not mostly provide you with the correct explanation. There are examiner reports which are pretty helpful for the MCQs but only with the recent papers. You may discuss the problems with your teacher or anyone over here.

 

[asadalam]

View attachment 34015
Circuit as shown in figure

Switch closed what happens?
Since capacitor is charging for some time all current falls on it but in the end does the bulb light up?
And does it light up continuosly or the capacitor discharges in process and hence the bulb blinks ?

Thanks in advance

The capacitor starts charging and the bulb also lights up along with it as long as switch is closed.However if switch is open the capacitor will provide the bulb with potential difference for some time,but it will become dim and then stop working.And it lights up continuously if the voltage is provided.