Chemistry: Post your doubts here!

[ZaqZainab]

dats not da volume, volume is 50 cm³
M = (moles × 1000)/V

Oh okay got it thanks can you help me out with the others

 

[Hadi Murtaza]

i can try, i'll do e z ones first.

 

[Hadi Murtaza]

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.31
.
Oxides of group 1 n group 2 metals r basic, as r most other metal oxides.
Mg salts r white usually.
MgO is ionic so high melting point.
All oxides r insoluble except group 1 oxides, Mg is not group 1 so D part is false

 

[ZaqZainab]

q.31
.
Oxides of group 1 n group 2 metals r basic, as r most other metal oxides.
Mg salts r white usually.
MgO is ionic so high melting point.
All oxides r insoluble except group 1 oxides, Mg is not group 1 so D part is false

opps i didn't know about the last point Thanks again

 

[Hadi Murtaza]

opps i didn't know about the last point Thanks again

I knw, Chem is all ratta

 

[Hadi Murtaza]

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.16
Adding aquoes nitric acid n silver nitrate will give white ppt. If u den add ammonia, ppt dissolves.
Answer: A

 

[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