Chemistry and Physics AS paper 12 MCQS

[ahmed abdulla]

Yaar I am not sure about 27. I mean i get confused between C and D.
Let me work it out and then i'll tell you too

help plz

 

[Aries_95]

help plz

which paper is this from?

 

[ahmed abdulla]

which paper is this from?

mj 2007 q. 34 & 9

 

[mehranshaikh]

Can someone explain this to me? I have done all the calculation but answer is coming different.
Summer 2011, Variant 13, Q12.

My calculation
Al2O3 + 6HCl = 2AlCl3 + 3H20

As 1 mol of Al2O3 reacts with 6 mol of HCl, 0.02 mol react with 0.12 mol.
0.12/2= 0.06 dm3 of HCl 60 cm3. Whats wrong with this?

 

[Aries_95]

Can someone explain this to me? I have done all the calculation but answer is coming different.
Summer 2011, Variant 13, Q12.

My calculation
Al2O3 + 6HCl = 2AlCl3 + 3H20

As 1 mol of Al2O3 reacts with 6 mol of HCl, 0.02 mol react with 0.12 mol.
0.12/2= 0.06 dm3 of HCl 60 cm3. Whats wrong with this?

View attachment 28685

The question says that there are 0.02 moles of Al not Al2O3.
My calculation:
4Al+3O2--->2Al2O3
AL2O3+6HCl---->2AlCl3
Since 4 moles of Al is equal to 2 moles of Al2O3, 0.02 moles of Al will be equal to 0.01 mole of Al2O3.
According to equation,
Moleos of HCl=6xmoles of Al2O3
i.e moles of Hcl=0.06.
since conc=mol/vol,
vol=mole/conc
=0.06/2=0.03 dm^3= 30 cm^3
The answer is C.

 

[ahmed abdulla]

The question says that there are 0.02 moles of Al not Al2O3.
My calculation:
4Al+3O2--->2Al2O3
AL2O3+6HCl---->2AlCl3
Since 4 moles of Al is equal to 2 moles of Al2O3, 0.02 moles of Al will be equal to 0.01 mole of Al2O3.
According to equation,
Moleos of HCl=6xmoles of Al2O3
i.e moles of Hcl=0.06.
since conc=mol/vol,
vol=mole/conc
=0.06/2=0.03 dm^3= 30 cm^3
The answer is C.

i guess the question are tough which i asked u

 

[Aries_95]

mj 2007 q. 34 & 9

For Q.9:
For reaction 1:
Kc=[X2Y]^2/[X2]^2[Y2]
for reaction 2:
Kc={[X2][Y2]^1/2}/[X2Y]
=1/[{(X2Y)^2/(X2)^2(Y2)}
the answer is A.

 

[ahmed abdulla]

For Q.9:
For reaction 1:
Kc=[X2Y]^2/[X2]^2[Y2]
for reaction 2:
Kc={[X2][Y2]^1/2}/[X2Y]
=1/[{(X2Y)^2/(X2)^2(Y2)}
the answer is A when you work it out further.

workout what
doing this is easy

 

[ahmed abdulla]

In which species does the underlined atom have an incomplete outer shell?
A Al 2Cl 6 B CH3+
C Cl 2O D H2Cl C•

 

[mehranshaikh]

The question says that there are 0.02 moles of Al not Al2O3.
My calculation:
4Al+3O2--->2Al2O3
AL2O3+6HCl---->2AlCl3
Since 4 moles of Al is equal to 2 moles of Al2O3, 0.02 moles of Al will be equal to 0.01 mole of Al2O3.
According to equation,
Moleos of HCl=6xmoles of Al2O3
i.e moles of Hcl=0.06.
since conc=mol/vol,
vol=mole/conc
=0.06/2=0.03 dm^3= 30 cm^3
The answer is C.

Thanks!

 

[Aries_95]

In which species does the underlined atom have an incomplete outer shell?
A Al 2Cl 6 B CH3+
C Cl 2O D H2Cl C•

Can you plz mention the year and the question no plz!

 

[Aries_95]

thnx..ques 27 also?

Look, since the C:H ratio is high, we can predict that benzene is present.
Since it is not readily oxidised by mild oxidising agents, we say that it is a tertiary alcohol. draw the structures and the only compound which produced by the dehydration of X is D.

 

[hope4thebest]

Yaar I am not sure about 27. I mean i get confused between C and D.
Let me work it out and then i'll tell you too

I think it has something to do with tertiary alcohal....there is possibility of tertiary alcohal in D which cannot be oxidised

 

[Aries_95]

I think it has something to do with tertiary alcohal....there is possibility of tertiary alcohal in D which cannot be oxidised

since the C:H ratio is high, we can predict that benzene is present.
Since it is not readily oxidised by mild oxidising agents, we say that it is a tertiary alcohol. draw the structures and the only compound which produced by the dehydration of X is D.

 

[hope4thebest]

since the C:H ratio is high, we can predict that benzene is present.
Since it is not readily oxidised by mild oxidising agents, we say that it is a tertiary alcohol. draw the structures and the only compound which produced by the dehydration of X is D.

agreed

 

[Aries_95]

agreed

 

[ahmed abdulla]

Can you plz mention the year and the question no plz!

may 2012 va'12
i dont think in the question paper they give extra thing
its just the sam e!

 

[hope4thebest]

Ans 2 and 3 only
But what is the logic?

 

[mehranshaikh]

View attachment 28690
Ans 2 and 3 only
But what is the logic?

1 cannot be as molecules have to join. The molecules can join in any fashion so it can be any number less than 1.

 

[Aries_95]

View attachment 28690
Ans 2 and 3 only
But what is the logic?

thia question drove me crazy and the answer was so simple.
Thank you mehranshaikh