Biology; Chemistry; Physics: Post your doubts here!

[Tharindu]

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)

Thanks a lot......DDDD I get it now.....

 

[Tharindu]

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)

How to give trophies in this forums??

 

[Tharindu]

according to the reaction?

Thanks I get it DD

 

[ayeshaK]

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?

Atleast u should try 4 graphs frm the latest years !! Specially for physics !!

 

[luckywang]

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

mean the correct is the inner one?

 

[Tharindu]

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?

Graphs won't affect you as long as you are good in maths

 

[asd]

mean the correct is the inner one?

I made the inner one, don't know whther it's correct or not.

 

[luckywang]

I made the inner one, don't know whther it's correct or not.

oh...

 

[ayeshaK]

http://www.xtremepapers.com/papers/...onal O Level/Biology (5090)/5090_w09_qp_1.pdf
Mcq no 38 help please ?
I got answer D but in mark scheme it is A

 

[SalmanPakRocks]

Ahan! I m doing ATP for chemistry! Insha'Allah would start physics soon.

 

[asd]

http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_w09_qp_1.pdf
Mcq no 38 help please ?
I got answer D but in mark scheme it is A

It's A. can't be D
You see, if any of the alleles I(A) or I(B) combines with I(O) it will lead to blood group A or B, respectively (because I(O) is recessive, I(A) and I(B) dominant). With option D, there is a possibility of getting a blood group B (when B combines with O). So D is not an option. Other options also have the possibilities of getting Blood group B. Only option left is A.

 

[Spidey21]

http://www.xtremepapers.com/papers/CIE/Cambridge International O Level/Biology (5090)/5090_w09_qp_1. pdf
Mcq no 38 help please ?
I got answer D but in mark scheme it is A

it has to be A it can never be D if it was D then the baby would have bg : A,B or AB!!

 

[Tharindu]

2 The labels fell off two bottles each containing a colourless solution, one of which was sodium carbonate solution and the other was sodium chloride solution.
The addition of which solution to a sample from each bottle would most readily enable the bottles to be correctly relabelled?
A ammonia
B hydrochloric acid
C lead(II) nitrate
D sodium hydroxide

Pls explain

 

[Spidey21]

2 The labels fell off two bottles each containing a colourless solution, one of which was sodium carbonate solution and the other was sodium chloride solution.
The addition of which solution to a sample from each bottle would most readily enable the bottles to be correctly relabelled?
A ammonia
B hydrochloric acid
C lead(II) nitrate
D sodium hydroxide

Pls explain

is it an MCQ??

 

[falcon678]

2 The labels fell off two bottles each containing a colourless solution, one of which was sodium carbonate solution and the other was sodium chloride solution.
The addition of which solution to a sample from each bottle would most readily enable the bottles to be correctly relabelled?
A ammonia
B hydrochloric acid
C lead(II) nitrate
D sodium hydroxide

Pls explain

the ans is (B) here cuz sodium carbonate comes in contct with HCl it will give off effervesnce(bubbling)....how ever sodium chloride will ve no reaction...!!!

 

[Tharindu]

the ans is (B) here cuz sodium carbonate comes in contct with HCl it will give off effervesnce(bubbling)....how ever sodium chloride will ve no reaction...!!!

Why do you need effervescence on this question???? I really don't understand this labels

 

[Spidey21]

the ans is (B) here cuz sodium carbonate comes in contct with HCl it will give off effervesnce(bubbling)....how ever sodium chloride will ve no reaction...!!!

somehow it does not feel right..:s

 

[asd]

Yea, the ans is B, and falcon gave the correct explanation.

 

[Spidey21]

Why do you need effervescence on this question???? I really don't understand this labels

tell the question and year plz...
i think it should be C btw.

it would a ppt reaction with NaCl with lead(2)cl will form white compunds..
and nothing would happen to the other one..

 

[falcon678]

Why do you need effervescence on this question???? I really don't understand this labels

yar itz like this ke on is NaCO3....while other is NaCl....n v need to differntiatie b/t the two so tht corect labls cld be postd..!!