Chemistry: Post your doubts here!

[sweetiepie]

Tips for #31-40 Chemistry MCQs
viewtopic.php?f=26&t=9156

 

[byhn222]

hey guys, i had a question, in an exam is it okay to go underneath the lines given to answer a question, if let's say you cross something out in your answer and change it so you need more space? and another question, in my paper 5 exam i had to draw a table, and i drew it in pencil, which i know is okay, but i filled in the headings with a pencil too. would i lose the marks?

 

[daisy1234]

Hey guys can u plz help?
on02 no.23,24,29,31 and 37.
Can u plz explain why that is the answer!

 

[panda222]

Hey guys can u plz help?
on02 no.23,24,29,31 and 37.
Can u plz explain why that is the answer!

What paper?

 

[panda222]

Oh yeah and how do you do question 2

http://www.xtremepapers.com/CIE/Interna ... _qp_11.pdf

 

[yubakkk]

urgnt-help
can-any-one-provide-me-marksheme-of-may-june-2002-and-oct-nov-2002
of-chemistry-paper-1??/
please-povide-me-if-u-have

 

[XPFMember]

Assalamoalaikum!!

urgnt-help
can-any-one-provide-me-marksheme-of-may-june-2002-and-oct-nov-2002
of-chemistry-paper-1??/
please-povide-me-if-u-have

June:2002 (first page)

Nov:2002 (second page)

 

[yubakkk]

2) As a simplification, an adult human can be considered to have a daily diet of 1.80 kg of
carbohydrate (empirical formula CH2O).
Which mass of carbon dioxide does a person produce each day if all the carbohydrate eaten is
digested and oxidised?
A 0.267 kg B 0.800 kg C 1.32 kg D 2.64 kg

 

[yubakkk]

35 When the yellow liquid NCl 3 is stirred into aqueous sodium hydroxide, the reaction that occurs
can be represented by the following equation.
2NCl 3(l) + 6NaOH(aq) → N2(g) + 3NaCl (aq) + 3NaOCl (aq) + 3H2O(l)
What will be the result of this reaction?
1 The nitrogen undergoes a redox reaction.
2 A bleaching solution remains after the reaction.
3 The final solution gives a precipitate with acidified silver nitrate.

ANS-IS-A
HOW-OPT-1-IS-CORRECT??

 

[sweetiepie]

Some Helpful Notes For Chemistry Paper 1!!!
http://www.creative-chemistry.org.uk/al ... /index.htm

Chemistry Reagents and conditions for reactions in organic chemistry
viewtopic.php?f=26&t=7013

Organic chemistry mindmap
viewtopic.php?f=26&t=8477

Tips for #31-40 Chemistry MCQs
viewtopic.php?f=26&t=9156

 

[inkheart]

As chemisry paper 1 june 2005 Q1

A pure hydrogen is used in bottled gas for cooking and heating.
when 10cm3 of the hydrocarbon is burned in 70cm3 of oxygen (an excess) the final gaseous mixture contains 30cm3 of carbon dioxide and 20cm3 of untreated oxygen.
All gaseous volumes were measured under identical conditions.What is the formula of the hydrocarbon?

A.C2H6 B.C3H6 C.C3H8 D.C4H10



so what is the answer and please show me the working.

 

[NehaKush]

Cyanohydrins can be made from carbonyl compounds by generating CN– ions from HCN in the
presence of a weak base.

In a similar reaction, –CH2CO2CH3 ions are generated from CH3CO2CH3 by strong bases.
Which compound can be made from an aldehyde and CH3CO2CH3 in the presence of a strong
base?
A CH3CH(OH)CO2CH3
B CH3CO2CH2CH(OH)CH3
C CH3CH2CH(OH)CH2CO2CH3
D (CH3)2C(OH)CH2CO2CH3

its nov2009 paper12..

 

[AAestar]

Ans: 1 and 2

Ans: C[/size

How to do the above questions? They are from Nov 08.

 

[karishma92]

5 Given the following enthalpy changes,
I2(g) + 3Cl2(g) → 2ICl3(s) ΔHo = –214 kJ mol–1
I2(s) → I2(g) ΔHo = +38 kJ mol–1
What is the standard enthalpy change of formation of iodine trichloride, ICl3(s)?
A +176 kJ mol–1
B –88 kJ mol–1
C –176 kJ mol–1
D –214 kJ mol–1

 

[Science]

N 07 P1 question 35. Please help me out someone.

 

[panda222]

is hydrogen bonding a van der wall force? SImple question

 

[AAestar]

is hydrogen bonding a van der wall force? SImple question

They are two different things. Hydrogen bond is stronger than the latter. Hydrogen bond is define as an electrostatic attraction between a hydrogen atom and an unshared pair of electron from a very electronegative atom such as NITROGEN, OXYGEN AND FLUORINE ( only these three).

 

[hikarigenzo]

Hi,help me pls with this question. Number 40. I really having a tough time doing organic chemistry question

http://www.xtremepapers.com/CIE/Interna ... _qp_13.pdf

I just need to know why the 1st choice is the answer. No matter how I drew it,I still get a chiral centre.

Your help is kindly appreciated.

Thanks

 

[Star-fire]

http://www.xtremepapers.com/CIE/Interna ... 5_qp_1.pdf
can some1 please explain question no.34....and

Which physical properties are due to hydrogen bonding between water molecules?
1 Water has a higher boiling point than H2S.
2 Ice floats on water.
3 The H−O−H bond angle in water is approximately 104°.

isn't number 3 suppose 2 be correct bcoz water has 105 angle?! but only 1 & 2 r correct

 

[Star-fire]

Hi,help me pls with this question. Number 40. I really having a tough time doing organic chemistry question

http://www.xtremepapers.com/CIE/Interna ... _qp_13.pdf

I just need to know why the 1st choice is the answer. No matter how I drew it,I still get a chiral centre.

Your help is kindly appreciated.

Thanks

1st choice doesn't contain chiral C the reason is when u oxidise the molecule given this is what u will get: 2 carboxylic acids on either side & the middle carbon is a ketone(carries double bond O) cannot be chiral.