Chemistry: Post your doubts here!

[not.maria]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s12_qp_11.pdf

Can someone explain Q 2, 9, 13 ,14, 22 and 36
Thanks!

Please someone help me out in this!
I am clueless

 

[Hadi Murtaza]

Please someone help me out in this!
I am clueless

Q.2
Taking out product between da reaction will increase da yield, but it wont have any effect on da rate.

 

[ZaqZainab]

Please someone help me out in this!
I am clueless

Q9

A: initial: 2 moles of P
equilibrium: x moles of R, therefore there must be 2x moles of Q (as the ratio of Q to R is 2:1). P will be 2-x moles (we subtract moles of R from moles of P since they are the same in equilibrium)
Add them up: x + 2x + 2 - x = 2x + 2 so A is incorrect

B: initial: 2 moles of P
equilibrium: x moles of R, therefore there must be 2x moles of Q (as the ratio of Q to R is still 2:1). P will be 2-2x moles (we subtract Q from P this time because P is the same as Q in equilibrium in this equation)
Add them up: x + 2x + 2 - 2x = x + 2 so B is the correct answer

I solved this question by considering each option one at a time.
Option B)
.......2P <=> 2Q + R
I.......2...........0.......0
C....-2x........+2x....+x
E....2-2x........2x......x

2-2x + 2x + x
= 2 + x

 

[ZaqZainab]

Please someone help me out in this!
I am clueless

Q14
first write down the equation
3Ba(NO3)2+10Al---->3N2+5Al2O3+3BaO

Mr of Ba(NO3)2 = 137 + 14*2 + 16* 6 = 261
looking at the mole ratio, 3 moles Ba(NO3)2 gives 3 moles N2.
moles of Ba(NO3)2= 3*10^-3
moles of N2= 3*10^-3
Moles=volume/24
Volume of N2= 0.072 dm^3
the options given are in cm^3
so 0.072*1000=72 cm^3

 

[Hadi Murtaza]

Please someone help me out in this!
I am clueless

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q1
Q11
Q13 how exactly?
Q14
Q16 doesn't it give white ppt?
Please help

Q.14
Equation
X(NO₃)₂ -------> XO + 2NO₂ + ½O₂

5/(X + 124) = (5 - 3.29)/(X + 16)
5(X + 16) = 1.71(X + 124)
5X + 80 = 1.71X + 212.04
5X - 1.71X = 212.04 - 80
3,29X = 132.04
[ X ≈ 40 ]

Calcium has da Mr of 40
Answer: B

 

[ZaqZainab]

Q.14
Equation
X(NO₃)₂ -------> XO + 2NO₂ + ½O₂

5/(X + 124) = (5 - 3.29)/(X + 16)
5(X + 16) = 1.71(X + 124)
5X + 80 = 1.71X + 212.04
5X - 1.71X = 212.04 - 80
3,29X = 132.04
[ X ≈ 40 ]

Calcium has da Mr of 40
Answer: B

omg this is so much to do this should be a 2 mark question in paper 2 instead or may be they should have given the Mr's at least to make it a little faster
thanks i got it now

 

[Hadi Murtaza]

omg this is so much to do this should be a 2 mark question in paper 2 instead or may be they should have given the Mr's at least to make it a little faster
thanks i got it now

I knw, took me a while too :/

 

[sweet.sugar]

Y

well i am not sure about 9 amd 11
25) it should be B na bcoz there are 3n carbon and 6n Hydrogen so if we balance the equation we get 9 moles of oxygen on the product side so for balancing the moles of oxygen in reactact obviously it should 4.5 because it already O2 so simple calculation for verfication --> 4.5 *2 ==> 9 so the overall equation is balanced
I hope you got it!

Yeah got it
Thanks

 

[not.maria]

Q.2
Taking out product between da reaction will increase da yield, but it wont have any effect on da rate.

I dont get it.
wont the equilibrium shift to the right hand side if ammonia i.e product is removed?

 

[Browny]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s04_qp_1.pdf

Can anyone explain question number 13 ans B, 28 ans D and 35 ans B.

Questions are;
In 13 why can't A be correct.
In 28 why is D correct, I think D is correct as tertiary alcohols don't oxidise even by strong oxidising agents right?
In 35 I don't get a point.

And in 19 is NO a reducing agent or not?

 

[ZaqZainab]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s04_qp_1.pdf

Can anyone explain question number 13 ans B, 28 ans D and 35 ans B.

Questions are;
In 13 why can't A be correct.
In 28 why is D correct, I think D is correct as tertiary alcohols don't oxidise even by strong oxidising agents right?
In 35 I don't get a point.

And in 19 is NO a reducing agent or not?

Q13 i have problems with equations too >.< but here i wouldn't have gone for A
lets look at other reaction of NaOH something you might be familiar with
like this one NaOH + НСl = NaCl + Н2О
why not NaClOH2?
Sulphur dioxide is acidic its just like HCl, it is weaker though
now you are left with B C or D
when acid+ base water is release
so not D and C isn't balanced
but i guess we need to learn this kind of equations
here is a link http://www.allreactions.com/index.php/group-1a/natrium/sodium-hydroxide just have a quick look
Q28 yes you are right
Q35
Carbon monoxide is neutral, and does not react like the other two acidic gases.

 

[papajohn]

It should be D. Why not D
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s09_qp_1.pdf
Q3 Why not not DDDDDD!

 

[sweet.sugar]

Q

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w06_qp_1.pdf
Q1
Q11
Q13 how exactly?
Q14
Q16 doesn't it give white ppt?
Please help

hey in the previous page i posted some same doubts n they got solved check them out
Q1 i can solve tht
The ans is A bcz we need to find the concentration so write the eq C = N multiply V
1.0*10^-2 multiplied by 25 = 0.25
0.25/50 (the water sample) = 5*10^-3
Ans in step 2/2 =2.5*10-3
Basically wt we did was c=n*v/water sample=ans/2
Hope u got it

 

[ZaqZainab]

Q

hey in the previous page i posted some same doubts n they got solved check them out
Q1 i can solve tht
The ans is A bcz we need to find the concentration so write the eq C = N multiply V
1.0*10^-2 multiplied by 25 = 0.25
0.25/50 (the water sample) = 5*10^-3
Ans in step 2/2 =2.5*10-3
Basically wt we did was c=n*v/water sample=ans/2
Hope u got it

yup i got all of them Hadi Murtaza solved them
thanks anyways

 

[papajohn]

It should be D. Why not D
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf
Q3 Why not not DDDDDD!

Please Zaq help

 

[ZaqZainab]

It should be D. Why not D
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf
Q3 Why not not DDDDDD!

if you notice it is in the 6th group and 2nd period
ther is only 1 element that is O(8)
1s2 2s2 2p3

Can you tell me how you think it is D?

 

[not.maria]

we

It should be D. Why not D
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_s09_qp_1.pdf
Q3 Why not not DDDDDD!

for the first four IE the difference is roughly 2000
between the 4th and 5th there is a difference of 3550.but the principal quantum number is still the same i.e the principal quantum no is 2.
the distance between 2p and 2s is small.while distance between 2s and 1s is large

 

[papajohn]

if you notice it is in the 6th group and 2nd period
ther is only 1 element that is O(8)
1s2 2s2 2p3

Can you tell me how you think it is D?

Last trend such a big difference?" 2p6 is stable,

 

[sweet.sugar]

yup i got all of them Hadi Murtaza solved them
thanks anyways

Thats gud
Got some (actually 6 ) q from m/j/06 :/
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s06_qp_1.pdf
Q1-D Q2-B Q10-C Q27-B Q38-B

 

[ZaqZainab]

we

for the first four IE the difference is roughly 2000
between the 4th and 5th there is a difference of 3550.but the principal quantum number is still the same i.e the principal quantum no is 2.
the distance between 2p and 2s is small.while distance between 2s and 1s is large

woh what i do is look for a huge change in the ionisation energy like here it is from 13300 to 71000
so basically the outer shell has 6 electron here cause the when we remove the 7th one is is most probably closer to the nucleus
and from the periodic table this element is in the 6th group
and they have mentioned from Li to Ne so 2nd period

Last trend such a big difference?" 2p6 is stable,

What do you mean ? yes it but where will you get those 2 extra electrons from this is for Ne