Chemistry: Post your doubts here!

[AbbbbY]

Textbook ? because i never saw a question from the textbook !

What question exactly are you talking about?
THere're no questions from the text book mate. That's precisely the point. -_-

 

[sitooon]

What question exactly are you talking about?
THere're no questions from the text book mate. That's precisely the point. -_-

how comes ? the nmr stuff and inhibitor and bonds and all that stuff are there in our textbook
but the design and drug part is always new question which are not related to what you study in the textbook!!

 

[AbbbbY]

how comes ? the nmr stuff and inhibitor and bonds and all that stuff are there in our textbook
but the design and drug part is always new question which are not related to what you study in the textbook!!

I don't even have a text book. ^_^

 

[sitooon]

I don't even have a text book. ^_^

OMG , then how do you study !! Give us the tip

 

[sumeru]

This link is taking me to Bio revision guide :S
http://ebookee.org/Mary-Jones-quot-...evel-Biology-Revision-Guide-quot-_998939.html

Really...haha, i have no idea why did that happen...here's the question...http://papers.xtremepapers.com/CIE/... AS Level/Chemistry (9701)/9701_s12_qp_51.pdf
Q.1...c(iii)

 

[AbbbbY]

OMG , then how do you study !! Give us the tip

I use the Cambridge factsheets. (link)
or, Chemguide.

Mostly chemguide though. Lovely lovely stuff there.

 

[sitooon]

I use the Cambridge factsheets. (link)
or, Chemguide.

Mostly chemguide though. Lovely lovely stuff there.

I wish i had the link by begining of my A levels , now the time is up

 

[sitooon]

MgBr2 , what is the product at Anode using electrode potential ? it should be Oxygen , but the Answer given is Bromine !?

 

[ahmed abdulla]

iv-
The decomposition will complete when the plunger stops moving outwards. You'll heat and reheat till the point comes when the plunger stops moving outwards.

v- You've to record the volume of gas collected. You've already calculated how much volume of gas a fixed mass of copper carbonate will give you. You've to simply relate the two here and state that whichever volume is equal, or close enough, to the theoretical value for the given mass (calculated in iii) shows you which equation it is following.

3d
I haven't completed the table so idk if any of the other calculated densities are 1.154. If they are, simply equate the ratio of H2SO4/H2O (or the other way round) in terms of water added to the one which has 1.154.
I mean, (40+X)/60 = Volume of water that makes 1.154 from the table/volume of H2SO4 that makes 1.154 from the table.

If there's no valuee 1.154 in the table, do this:
Calculated Density = Mass of H2O + H2SO4 / Total Volume
Equate this to 1.154


1.154 = (60+X)/32.859+(1.003X)
Solve for X. I simple plugged it into my calculator saving me the time and got X = 140.23
X - volume originally added = volume required
140.23 - 40.00 = 100.23 cm3 required.

Please check the marking scheme and let me know if this is incorrect. The answer.


Explaining my 1.003X,

from the equation, we can see that 40g of H2O = 40.12cm3. So, 1g = 1.003 cm3.
Let me know if this doesn't make sense. I'm not good at explaining.

3e
mass error = 0.01/100 * 100 = 0.01%
volume error =
100g of H2SO4 = 54.765cm3
0.25/54.765*100 = 0.456%

Your answers are all right , Thanks

 

[AbbbbY]

I wish i had the link by begining of my A levels , now the time is up

Tis never too late!

And, I've posted that link on this thread several times!
Besides, believe in yourself. So what if you didn't have the link etc. You prepared for your exam using YOUR way. Good enough innit.

 

[sitooon]

Tis never too late!

And, I've posted that link on this thread several times!
Besides, believe in yourself. So what if you didn't have the link etc. You prepared for your exam using YOUR way. Good enough innit.

You are just awesome

 

[AbbbbY]

MgBr2 , what is the product at Anode using electrode potential ? it should be Oxygen , but the Answer given is Bromine !?

Br2 + 2e <=> 2Br- +1.07
O2 + 4H+ + 4e <=> 2H2O +1.23

The oxygen reaction will go forward, the Bromine reaction will go backwards. Br2(g) will be evolved.

 

[sitooon]

Br2 + 2e <=> 2Br- +1.07
O2 + 4H+ + 4e <=> 2H2O +1.23

The oxygen reaction will go forward, the Bromine reaction will go backwards. Br2(g) will be evolved.

Ok check this:
Fe2+ + 2e– ⇌ Fe -------------------- –0.44
O2 + 4H+ + 4e– ⇌ 2H2O --------- +1.23
first reaction will be reversed , so Fe2+ is produced not oxygen !

 

[Browny]

http://papers.xtremepapers.com/CIE/...d AS Level/Chemistry (9701)/9701_w04_qp_1.pdf

Can anyone please explain questions 5,7,12 and 18?

 

[Browny]

Who's doing chemistry paper 33?

 

[robinhoodmustafa]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w04_qp_1.pdf

Can anyone please explain questions 5,7,12 and 18?

5. The state with the most parallel spins is the lowest energy configuration. Refer "Hund's rule" Answer is C

7. Forces act between two molecules or atoms as a result of their size.this force increases with the increase in size of the particle. we wont choose any other option because it involves the sharing and donating of electron and form a strong bond between the molecule and that is the reason it reacts to form a new bond . answer

 

[Young Stunner]

1- N is going from +3 to 0
2- NaOCl is a bleach
3- NaCl will give you a ppt with AgNO3. P3 review!

Thanks but how is Nitrogen undergoing a REDOX reaction. I can see a reduction only?
And do we have to memorize all the reactions from P3

 

[Jinosupreme]

Guys need help, I get A why it is coplanar, but not B,C,D,E? Why??

 

[AbbbbY]

Guys need help, I get A why it is coplanar, but not B,C,D,E? Why??

Good lord! This is the fifth time I've seen this question here in the last 10 days.

I'll just quote a previous response of mine.

ON09 42 Q5a.
I've answered this before a day or two ago but I'll do it again anyway.
Look. This stuff isn't in the syllabus or taught. This is precisely why it has shown you the 4 figures above the actual question. The examiner wants you to analyze those figures, see whats going on, and apply THAT to the question.

The question shows that all carbons in Benzene can be made to lie on the same plane, but not in cyclohexane. The question also shows that butane Carbons can be made to lie on the same plane, but methylpropane, also an alkane, cannot.
This tells us that if a compound has a ring, OR branching, it cannot be made to lie on the same plane.

All of them are co-planer apart from B.

C is coplaner because you don't have to consider the Oxygen atoms. The others are unbranched and two individual chains lying on the same plane.
Get it?

 

[sitooon]

on Which cases we put the product at anode ?
E0 is not always true ! check!