Chemistry: Post your doubts here!

[user]

Flask X contains 5 dm3 of helium at 12 kPa pressure and flask Y contains 10 dm3 of neon at 6 kPa
pressure.
If the flasks are connected at constant temperature, what is the final pressure?
A 8 kPa B 9 kPa C 10 kPa D 11 kPa

Ans is A ??

aoa wr wb!

use this eqn:

P1V1 = P2V2

5 x 12 + 6 x 10 = (10 + 5) x p
p =8

 

[Student12]

Assalamoalaikum wr wb!

Since when is gaseous bromine purple...

This question is from N'10_12 Q 18

View attachment 8951

Isnt the answer B ?

 

[user]

Isnt the answer B ?

sorry ms says its D
lemme edit the pic

 

[mushoo]

the number of moles polymers therotically can never be equal to the number of moles of monomer.....so 1 is not the answer thus only option is C

yeah.ryt.

but do u have any explainatn fr this?? -_-

 

[hm12]

Ah, so there are 6? Thanks a lot, I appreciate the effort.

looks like there are 6 i hope i am right though

 

[KurayamiKimmi]

Assalamoalaikum wr wb!

Since when is gaseous bromine purple...

This question is from N'10_12 Q 18

View attachment 8952

its not
and the answer is B i think

 

[Goku]

Thanks so does that mean when KMnO4 oxidises alchohol to carboxylic acids and ketones respectively it is turned from orange to green? Therefore it gets reduced?

Dude manganate is purple! :/

 

[Goku]

-Start backwards. It saves time.
-Use process of elimination. You may not know what is correct, but you might know what is wrong, so don't worry about those options and focus on the others. (Especially useful in the last 10 questions)
-Use trial and error. Where possible, plug in the values from answers, and work the equation backwards to figure out which one is correct.

thankyoou!!
I loved the last tip! gonna try it.
and I always start the paper back words

 

[Student12]

Assalamoalaikum wr wb!

Since when is gaseous bromine purple...

This question is from N'10_12 Q 18

View attachment 8952

http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w10_ms_12.pdf
its B ? :S

 

[user]

http://www.xtremepapers.com/papers/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_ms_12.pdf
its B ? :S

probably i'm mistaken

 

[mushoo]

its not
and the answer is B i think

the ans is B ofcrse
as the air is almst of nitrogen and oxygen,
and O2 = 32
N2 = 28
total mass = 60.

while Br2 itself is 160.
threfre its simply denser than air! :/

 

[KurayamiKimmi]

the ans is B ofcrse
as the air is almst of nitrogen and oxygen,
and O2 = 32
N2 = 28
total mass = 60.

while Br2 itself is 160.
threfre its simply denser than air! :/

exactly ​

 

[KurayamiKimmi]

Moreover if you google images of bromine vapour -you can see it's reddish brown not purple

 

[mushoo]

Kimmi pls try ths ques.:/

A monomer undergoes addition polymerization.A 1 mol sample of the monomer is completely polymerized.
How many moles of polymer might , theoretically, be formed?
1. 1
2. 10^-6
3. 1/ 6.02*10^23 (1/ Avogadro's cons.)

the ans is C, cox 1 is nt the ans.
but hw cum the ans are 2 &3 ??

 

[nerdybookworm]

URGEEEEEENNNTTTTTTTT...OCTO NOV...2011 VARIENT 11 PAPER 1...Q 6,914,15,20,23,25,28,29...plzz....


http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_11.pdf

 

[Student12]

When ethanal, CH3CHO, reacts with HCN and the organic product is hydrolysed by aqueous
acid, organic compound Y is formed.
When propanal, C2H5CHO, is heated under reflux with acidified potassium dichromate(VI),
organic compound Z is formed.
What is the difference in relative molecular mass of compounds Y and Z?
A 12 B 14 C 16 D 17

how is it C ?

 

[user]

Moreover if you google images of bromine vapour -you can see it's reddish brown not purple

nopes..i knew that...!

i don't know what's wrong i downloaded these papers before the site update..and the ms i have says its D

check the attachment..

 

[mushoo]

URGEEEEEENNNTTTTTTTT...OCTO NOV...2011 VARIENT 11 PAPER 1...Q 6,914,15,20,23,25,28,29...plzz....


http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_w11_qp_11.pdf

see, we just have to divide the energy that is given by 6.
cos while the have broken N-F bond 6 tyms, so simply divide it by 6 to get the bond energy fr 1! -_-

 

[gary221]

Hey any idea how 2 solve this??

Ans is C

 

[Zsiddiqui]

question 11 and 23 :/
http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_s11_qp_12.pdf
http://www.xtremepapers.com/papers/... AS Level/Chemistry (9701)/9701_s11_ms_12.pdf