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

Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #615 on: May 31, 2011, 08:46:37 pm »
Quote from: BabuRao GanpatRao Aaapte on May 31, 2011, 08:45:08 pm
i got it 24.35 and in the periodic tabel it is 24.3 , i think choosing the closest one would be best
and thus the ans would have been 24.1 as  it it is the closest to 24.35, see the examinaer REPORT, somtinh would be mentioned there
lol I checked the website.... And the answer is 24.8...Definitely a mistake... :) Its none of the above Vin :P
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Offline Aadeez || Zafar

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #616 on: May 31, 2011, 08:49:26 pm »
hw cn it be 24.8, we have to calculate the ans from data provide and not frmthe website

using the dat

i get atomic mass of Mg to be= 1900/78

no mistake in MS
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Yeh BaaabuRaao ka style hein!

Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #617 on: June 01, 2011, 09:47:28 am »
Quote from: BabuRao GanpatRao Aaapte on May 31, 2011, 08:49:26 pm
hw cn it be 24.8, we have to calculate the ans from data provide and not frmthe website

using the dat

i get atomic mass of Mg to be= 1900/78

no mistake in MS
dude am talking abt the answer on the website is 24.8..I know its 24.35..Check my working above..
I meant there is a mistake on the website answers thts all  ;D
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Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #618 on: June 01, 2011, 12:22:02 pm »
November 2009 V1..Question 19
                             Question 21 : Confused between A and C....
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #619 on: June 01, 2011, 12:35:13 pm »
Quote from: SkyPilotage on June 01, 2011, 12:22:02 pm
November 2009 V1..Question 19
                             Question 21 : Confused between A and C....
but which paper
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Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #620 on: June 01, 2011, 12:48:27 pm »
Quote from: EMO123 on June 01, 2011, 12:35:13 pm
but which paper
what do you think? :P Paper 1 dude :)
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Offline angel_ak

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #621 on: June 01, 2011, 01:46:42 pm »
ammonium nitrate NH4NO3, can decompose explosively when heated.

NH4NO3 ----------------> N2O + 2H2O

what are the changes in the oxidation num of the two N atoms in NH4NO3 when this reaction proceeds?

1. -2, -4
2. +2, +6
3. +4, -6
4. +4, -4
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Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #622 on: June 01, 2011, 01:57:25 pm »
Quote from: angel_ak on June 01, 2011, 01:46:42 pm
ammonium nitrate NH4NO3, can decompose explosively when heated.

NH4NO3 ----------------> N2O + 2H2O

what are the changes in the oxidation num of the two N atoms in NH4NO3 when this reaction proceeds?

1. -2, -4
2. +2, +6
3. +4, -6
4. +4, -4
Do it stepwise...
-Oxidation number of N in NH4+ is -3 because 4H have oxidation number of +4 ANd the overall charge is 1+...
-Oxidation Number of N in NO3- is +5 because 3O have oxidation number of -6 And the overall charge is 1-....
-Oxidation number of N in N20 is +1 because O has an oxidation number of -2 And the overall charge is 0...
So from -3 to +1 is +4 and from +5 to +1 is -4..Therefore the answer is D... :)
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Offline aloha32

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #623 on: June 01, 2011, 03:23:37 pm »
Hi could anyone plz heth Nov 08 P1 Q1, 2 and 3?
Often the first onez always seem to be wierd calculations onez as compared to the rest of the paper
Thank you! :)
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Offline angel_ak

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #624 on: June 01, 2011, 05:17:22 pm »
THANKEW!!  ;D

0.200 mol of a hydrocarbon undergo complete combustion to give 35.2g of carbon dioxide and 14.4g of water as the only products. what is the molecular formula of the hydrocarbon?
1. C2H4
2. C2H6
3. C4H4
4. C4H8
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #625 on: June 01, 2011, 05:28:30 pm »
Quote from: angel_ak on June 01, 2011, 05:17:22 pm
THANKEW!!  ;D

0.200 mol of a hydrocarbon undergo complete combustion to give 35.2g of carbon dioxide and 14.4g of water as the only products. what is the molecular formula of the hydrocarbon?
1. C2H4
2. C2H6
3. C4H4
4. C4H8
for this we get a ratio of 1:2
but there are two options of 1:2 haydrocarbons
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Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #626 on: June 01, 2011, 05:33:50 pm »
Quote from: EMO123 on June 01, 2011, 05:28:30 pm
for this we get a ratio of 1:2
but there are two options of 1:2 haydrocarbons
1:4 ratio...
N of Co2 = 35.2/44 = 0.8
N of H20 = 14.4/18 = 0.8
So ratio of CxHy:CO2:H2O
                  1   :   4  :  4
So there are 4 C and 8 H and 12O so  the Hydrocarbon iS C4H8...
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Offline Vin

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #627 on: June 01, 2011, 05:38:38 pm »
18 A solid nitrate fertiliser reacts with an alkali to produce a gas which turns damp pH paper blue.

What is the empirical formula of this fertiliser?

A NO3 B NHO3 C NH2O D N2H4O3


D. How and why? :/
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Offline SkyPilotage

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #628 on: June 01, 2011, 05:56:19 pm »
Quote from: Vin on June 01, 2011, 05:38:38 pm
18 A solid nitrate fertiliser reacts with an alkali to produce a gas which turns damp pH paper blue.

What is the empirical formula of this fertiliser?

A NO3 B NHO3 C NH2O D N2H4O3


D. How and why? :/
Ammonium salts + alkalis -----> ammonia gas...
So its NH4NO3 which has the molecular formule N2H4O3...
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Offline EMO123

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Re: ALL CIE CHEMISTRY DOUBTS HERE !!
« Reply #629 on: June 01, 2011, 06:07:20 pm »
Quote from: SkyPilotage on June 01, 2011, 05:33:50 pm
1:4 ratio...
N of Co2 = 35.2/44 = 0.8
N of H20 = 14.4/18 = 0.8
So ratio of CxHy:CO2:H2O
                  1   :   4  :  4
So there are 4 C and 8 H and 12O so  the Hydrocarbon iS C4H8...
i am sorry to say but if the ratio is 1:4 then it will be C4H16
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