Chemistry: Post your doubts here!

[afsah shaikh]

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_11.pdf
Q 34, 35 and 36 plz

 

[Es Jay]

oct/nov 11 p11, quest 16.
working please?

 

[M.Kabir Nawaz]

When carboxylic acid does nucleophilic substitution reaction it form Acid halides. RCx=O. Why can not we call it halogeno aldehydes.?

 

[jinjanet]

an organic compound will decolorise dilute acidified aqueous potassium manganate(VII) on warming, but will not decolorise bromine water.
what could the organic compound be?
A. butane B. ethanol C. ethene D. ethanoic acid

 

[PhyZac]

an organic compound will decolorise dilute acidified aqueous potassium manganate(VII) on warming, but will not decolorise bromine water.
what could the organic compound be?
A. butane B. ethanol C. ethene D. ethanoic acid

I think the answer is B

 

[snowbrood]

When the salt (C2H5)4N+Cl- is treated with hydrogen chloride a white ionic solid X is formed.
When X is dissolved in water a 20cm^3 sample of the solution requires 24cm^3 of 0.1moldm^-3 Naoh for neutralization.

Another 20cm^3 sample of the solution requires 48cm^3 of 0.1 moldm^-3 AgNO3 for complete precipitation of chloride of AgCl.

What do these data show the formula of the anion in X to be.
(A) HCl2- (b) HCl3^2-
(C) HCl4^3- (D) H2Cl3-
E H2Cl5^-3.

Correct answer is A
littlecloud11,scouserlfc

 

[Amy Bloom]

an organic compound will decolorise dilute acidified aqueous potassium manganate(VII) on warming, but will not decolorise bromine water.
what could the organic compound be?
A. butane B. ethanol C. ethene D. ethanoic acid

Its B

 

[syed1995]

an organic compound will decolorise dilute acidified aqueous potassium manganate(VII) on warming, but will not decolorise bromine water.
what could the organic compound be?
A. butane B. ethanol C. ethene D. ethanoic acid

It's definitely B.

The only one out of those which can get Oxidized are B and C.. since it didn't decolourize Br2 it doesn't have a C=C double bond so it's not ethene. Answer is B.

 

[snowbrood]

an organic compound will decolorise dilute acidified aqueous potassium manganate(VII) on warming, but will not decolorise bromine water.
what could the organic compound be?
A. butane B. ethanol C. ethene D. ethanoic acid

In the context of the A level syllabus, only two acids can be oxidized, and that is methanoic acid and ethanedioic acid (COOHCOOH also knows as oxalic acid). In the presence of acidified aqueous KMNO4, it will be oxidized to produce carbon dioxide and water.
ethanoic acid is acetic acid so it cant be oxidized only ethanol can be oxidized and will not decolorize bromine water

 

[littlecloud11]

When the salt (C2H5)4N+Cl- is treated with hydrogen chloride a white ionic solid X is formed.
When X is dissolved in water a 20cm^3 sample of the solution requires 24cm^3 of 0.1moldm^-3 Naoh for neutralization.

Another 20cm^3 sample of the solution requires 48cm^3 of 0.1 moldm^-3 AgNO3 for complete precipitation of chloride of AgCl.

What do these data show the formula of the anion in X to be.
(A) HCl2- (b) HCl3^2-
(C) HCl4^3- (D) H2Cl3-
E H2Cl5^-3.

Correct answer is A
littlecloud11,scouserlfc

No of moles of NaOH = 48/1000 * .1 = 2.4* 10^-3
one mole OH- ions react with one mole H+ ions. So the no. of moles of H+ ions present in the solution of X was 2.4* 10^-3

No of moles of AgNO3 = 48/1000* .1 = 4.8* 10^-3
One mole of Ag+ ions react with one mole of Cl- ions. So the no. of moles of Cl- ions in X is 4.8* 10^-3

Now find the ratio of H+ to Cl- ions
2.4* 10^-3/4.8* 10^-3 = 1:2
the only answer which follows this ratio is A.

 

[yousef]

Hi everyone, AsSalamoAlaikum Wr Wb..

To get things organized in a better way, I am making this thread. As othewise, some queries remain unanswered!

So post your CHEMISTRY doubts in this thread. InshaAllah members around will help you.

Any Chemistry related notes and links will be added here in this post. Feel free to provide the links to your notes around the forum, or any other websites!

Chemistry Notes:


http://www.chemguide.co.uk This is the website, which contains almost everything classified according to the syllabus.

Tips for solving chemistry MCQs 9701/01

Chemistry P5 Tips and Notes

Some links & Notes - by 'destined007'

Chemistry worksheets Link shared by hassam

Chemistry Application Booklet: Mistakes and Corrections!

Calculations for A level Chemistry, author E.N. Ramsden third edition ebook download.


Regards,
XPC Staff.

salam ... can any one plz answer the first question for this year ... i started with this and i really got disappointed with my fist quetion in the first paper >>> http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s03_qp_2.pdf qp1 ??

 

[snowbrood]

littlecloud11
To Identify oxide of nitrogen 0.1 mol of oxide is mixed with an excess of hydrogen and passed over a catalyst at suitable temperature
NxOy + H2 on heating with catalyst gives xNH3 +yH2O
the produced weighs 7.2g the ammonia produced is neutralized by 200cm^3 of 1.0 moldm^-3 Hcl
what is the formula of the oxide of nitrogen
tell me why the answer is N2O4

 

[djmohammad]

Which of the following molecules has no permanent dipole?
C2H5Cl or C2Cl4??
please help... also give me the reason

 

[lyuchenqujoy]

mj/08 qp1
question 27: please tell me how to judge between the answer C&D
question 38: please tell me what happens during these process
http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s08_qp_1.pdf

Thx a lot!!!!

 

[lyuchenqujoy]

Which of the following molecules has no permanent dipole?
C2H5Cl or C2Cl4??
please help... also give me the reason

C2Cl4
it will be helpful if you draw the structure( C=C , and each has 2 Cl bonded) and this molecule is symmetrical so there's no difference between the electronegtaivities so no permanent dipole..

 

[ashiqbal]

Q6
http://papers.xtremepapers.com/CIE/Cambridge%20International%20A%20and%20AS%20Level/Chemistry%20(9701)/9701_w11_qp_11.pdf

the answer i am getting is (C)1.62, but the marking scheme says (D) 2.89
can anyone explain how?

 

[Amy Bloom]

Q6

http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_w11_qp_11.pdf

the answer i am getting is (C)1.62, but the marking scheme says(D) 2.89
can anyone explain how?

Here u are. hope it helped

 

[jinjanet]

which ions are present in a solution of ethanol in an excess of concentrated sulphuric acid?
1 CH3CH2O-
2 CH3CH2OH2
3 HSO4-
explain

 

[yousef]

It's definitely B.

The only one out of those which can get Oxidized are B and C.. since it didn't decolourize Br2 it doesn't have a C=C double bond so it's not ethene. Answer is B.

In the context of the A level syllabus, only two acids can be oxidized, and that is methanoic acid and ethanedioic acid (COOHCOOH also knows as oxalic acid). In the presence of acidified aqueous KMNO4, it will be oxidized to produce carbon dioxide and water.
ethanoic acid is acetic acid so it cant be oxidized only ethanol can be oxidized and will not decolorize bromine water

salam ... can any one plz answer the first question for this year ... i started with this and i really got disappointed with my fist quetion in the first paper >>>http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_s03_qp_2.pdf qp1 ??

 

[daredevil]

Down the group the oxidising ability increase, thus down the group the better reducing agents.

Ummm i seriously think u're wrong abt that bcz. If it has a high oxidising ability it means that it oxidises well means its a good oxidising agent. So dont say that down the group are better reducing aggents bcz technically they r just poor oxidising agents. Link it with the electron give take concept of redox or it will bw confusing.
E.g there r bad conductors and good conductors and then there r insulators. U cant say that relatively poor conductors are insulators. Just keep to the basic concept bcz chem is confusing enough as it is right??
I hope u all get it now Rahma Abdelrahman