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Author Topic: ALL CIE CHEMISTRY DOUBTS HERE !!  (Read 122923 times)

Offline Master_Key

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #495 on: May 05, 2011, 12:15:49 pm »
Quote from: Fidato on May 05, 2011, 10:46:42 am
Question 1 please.

http://www.xtremepapers.me/CIE/International%20A%20And%20AS%20Level/9701%20-%20Chemistry/9701_w06_qp_1.pdf


Answer is A.

required 25 cm3 of 1.0 × 10–2 mol dm–3 potassium hydroxide for complete neutralisation.

moles = .025*1.0 × 10–2

=2.5 × 10-4 moles.


Ca2+ = 2H+

= 2.5 × 10-4 * 0.5 moles of Ca2+.

= 1.25 × 10-4 moles of Ca2+ in .05 dm3.

C = m/v

         1.25 × 10-4
C  =  ---------------
                0.05

C = 2.5 × 10-3
« Last Edit: May 05, 2011, 03:32:52 pm by Fidato »
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Offline Vin

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #496 on: May 05, 2011, 12:26:02 pm »
^Yep I got that too
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Offline Arthur Bon Zavi

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #497 on: May 05, 2011, 03:33:47 pm »
Quote from: Master_Key on May 05, 2011, 12:15:49 pm
Answer is A.

required 25 cm3 of 1.0 × 10–2 mol dm–3 potassium hydroxide for complete neutralisation.

moles = .025*1.0 × 10–2

=2.5 × 10-4 moles.


Ca2+ = 2H+

= 2.5 × 10-4 * 0.5 moles of Ca2+.

= 1.25 × 10-4 moles of Ca2+ in .05 dm3.

C = m/v

         1.25 × 10-4
C  =  ---------------
                0.05

C = 2.5 × 10-3

I didn't see the ratio as 2 : 1 and so didn't divide. Thanks.
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #498 on: May 06, 2011, 05:35:15 am »
i got one fantastic doubt
M/J 2002 P1 Q32 :)
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Offline Arthur Bon Zavi

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #499 on: May 06, 2011, 05:53:19 am »
Quote from: EMO123 on May 06, 2011, 05:35:15 am
i got one fantastic doubt
M/J 2002 P1 Q32 :)

H2O (2 bonding pairs, 2 lone pairs) = 104.5o
CH4 (4 bonding pairs) = 109.5o
NH3 (3 bonding pairs, 1 lone pair) = 107o
SF6 (6 bonding pairs. S has 12 electrons now, after bonding) = 90o
CO2 (linear) = 180o
BF3 (3 bonding pairs. Look at the number of electrons in the outer shell of B after bonding !) = 120o

Do the rest yourself, you may find answer as D.
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #500 on: May 06, 2011, 08:01:51 am »
Quote from: Fidato on May 06, 2011, 05:53:19 am
H2O (2 bonding pairs, 2 lone pairs) = 104.5o
CH4 (4 bonding pairs) = 109.5o
NH3 (3 bonding pairs, 1 lone pair) = 107o
SF6 (6 bonding pairs. S has 12 electrons now, after bonding) = 90o
CO2 (linear) = 180o
BF3 (3 bonding pairs. Look at the number of electrons in the outer shell of B after bonding !) = 120o

Do the rest yourself, you may find answer as D.
are you shure :-\
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Offline I like cheese

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #501 on: May 06, 2011, 08:58:09 am »
So ive done almost all the past papers...and now the qns which i dont know how to do have piled up

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_w05_qp_1.pdf

(Oct/Nov 2005 paper 1)
qn. 7,12,16,25

-----------------------------------------------------------------------------------------------------------------------------------------

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_w04_ms_1.pdf

(Oct/Nov 2004 paper 1)
Qns. 3,7,10,12,18, and why isnt the answer to Qn 27 Option B ???
-----------------------------------------------------------------------------------------------------------------------------------------

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_s06_qp_1.pdf

(May/June 2006 paper 1)

Qn 2,38
-----------------------------------------------------------------------------------------------------------------------------------------

not asking someone to do it all but if a couple of people could do 1 or 2 qns at a time that would be awesome  ;D ;D ;D ;D ;D ;D ;D ;D :P
« Last Edit: May 06, 2011, 09:02:56 am by I like cheese »
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Offline Master_Key

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #502 on: May 06, 2011, 01:59:56 pm »
Quote from: I like cheese on May 06, 2011, 08:58:09 am
So ive done almost all the past papers...and now the qns which i dont know how to do have piled up

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_w05_qp_1.pdf

(Oct/Nov 2005 paper 1)
qn. 7,12,16,25

-----------------------------------------------------------------------------------------------------------------------------------------

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_w04_ms_1.pdf

(Oct/Nov 2004 paper 1)
Qns. 3,7,10,12,18, and why isnt the answer to Qn 27 Option B ???
-----------------------------------------------------------------------------------------------------------------------------------------

http://www.xtremepapers.me/CIE/index.php?dir=International%20A%20And%20AS%20Level/9701%20-%20Chemistry/&file=9701_s06_qp_1.pdf

(May/June 2006 paper 1)

Qn 2,38
-----------------------------------------------------------------------------------------------------------------------------------------

not asking someone to do it all but if a couple of people could do 1 or 2 qns at a time that would be awesome  ;D ;D ;D ;D ;D ;D ;D ;D :P

(Oct/Nov 2005 paper 1)
qn. 7,12,16,25

7. Strong acid-strong base will have maximum negative change in enthalpy and Weak-Strong will have lower. So ans is A.

12. MgO = 1:1
     Al2O3 = 2:3
     SO2= 1:2

Plot your graph and you will get D.

16.Colourless gas = CO2 So a carbonate is sure. MgO and Bao react vigorously.

25. 2,4-dnph reacts with aldehydes.
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Offline I like cheese

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #503 on: May 06, 2011, 02:30:37 pm »
Quote
(Oct/Nov 2005 paper 1)
qn. 7,12,16,25

7. Strong acid-strong base will have maximum negative change in enthalpy and Weak-Strong will have lower. So ans is A.

12. MgO = 1:1
     Al2O3 = 2:3
     SO2= 1:2

Plot your graph and you will get D.

16.Colourless gas = CO2 So a carbonate is sure. MgO and Bao react vigorously.

25. 2,4-dnph reacts with aldehydes.

ok thanks man but ummmm for qn 25, in both options A and D , there is 1 aldehyde......so which one??? and does a carboxylic acid react with PCl5??
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #504 on: May 06, 2011, 03:21:35 pm »
master_key
2,4-dinitrophenaylhydrazine also reacts with ketones to give a deep yellpw pr orange precipitate

there fore
y is a aldehyde
so there is only one aldehyde not ketone also present in that combination

:. D is the right answer

hope i helped
« Last Edit: May 06, 2011, 03:27:13 pm by EMO123 »
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #505 on: May 06, 2011, 03:44:42 pm »
(Oct/Nov 2004 paper 1)
q-3
10cm3 of CH3SH
60cm3 of 3O2

so 70cm3 of total solution

now as water is already water at room temprature
so remove it from it

so you will get 50cm3

hope it works for you
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #506 on: May 06, 2011, 04:06:33 pm »
in the attachment full summary of shapes
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #507 on: May 06, 2011, 04:10:45 pm »
(Oct/Nov 2004 paper 1)
q-10

as there are 2 molecules of H
:. it is (0.20*1)/1.1
and 1 molecule of oxygen
:. it is (0.10*1)/1.1

:. answer is D
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #508 on: May 06, 2011, 04:17:56 pm »
(Oct/Nov 2004 paper 1)
q-12

the energy is added more to increase the proportion of molecules
this energy is activation energy

i think it is not right anyone plzz check this answer
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #509 on: May 06, 2011, 06:31:44 pm »
an i also have doubt
from
(Oct/Nov 2004 paper 1)
q-18,27
(May/June 2006 paper 1)
q-2,38
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