Chemistry: Post your doubts here!

[Awesome12]

http://studentbounty.com/pastpapers.../Chemistry (9701)/2011 Jun/9701_s11_qp_12.pdf

Question 26?

 

[Mayarzawaydeh]

http://studentbounty.com/pastpapers/Cambridge International Examinations (CIE)/International AS and A Level/Chemistry (9701)/2011 Jun/9701_s11_qp_12.pdf

Question 26?

the Answer is D.
possible isomers are:
1. CH2=CHCH2CH2CH3
2. CH3CH=CHCH2CH3 <--- the cis isomer.
3. CH(CH3)=CH(C2H5) <--- the trans isomer.
4. CH2=C(C2H5)CH3
5. CH2=C(CH3)CH2CH3
6. CH3C(CH3)=CHCH3

 

[Sarosh Jameel]

SOMEONE !

 

[princess Anu]

what will be the structure of ClF4-?

Each F only needs one more electron, they can't accept a lone pair from the Cl atom.

One simple guideline is to explore the possibility of a covalent bond first before considering using dative bonds.

 

[princess Anu]

How to name organic compounds with more than one functional group?
which functional groups are chosen as to give them the least number? and is it necessary for both or all of the functional groups to be on the longest chain ?

 

[princess Anu]

SOMEONE !

30 C?
28 D?
37 A?

and the last one D?

 

[Metanoia]

what will be the structure of ClF4-?

ClF4(minus1).gif

 

[Metanoia]

How to name organic compounds with more than one functional group?
which functional groups are chosen as to give them the least number? and is it necessary for both or all of the functional groups to be on the longest chain ?

When there are more than 1 functional groups, there is a need to rank the functional groups.

http://www.masterorganicchemistry.co...-nomenclature/

 

[Lola_sweet]

http://maxpapers.com/wp-content/uploads/2012/11/9701_s09_qp_2.pdf
variant 1
qs 2)ii) Why do we add to find the enthalapy change? why nt subtract?

 

[Metanoia]

http://maxpapers.com/wp-content/uploads/2012/11/9701_s09_qp_2.pdf
variant 1
qs 2)ii) Why do we add to find the enthalapy change? why nt subtract?

 

[Lola_sweet]

View attachment 52365

Thank u

 

[princess Anu]

When there are more than 1 functional groups, there is a need to rank the functional groups.

http://www.masterorganicchemistry.co...-nomenclature/

suppose if there is a compound with carboxylic acid and ketone group.. so I'll try to name as such both the functional groups are a part of the longest chain..? and if thats not possible, at least carboxylic acid should be .. right?

Moreover what's the use of the prefix??? for example ester prefix is ''oxycarbonyl'' and aldehyde's is OXO but we do not use these terms to name esters/aldehydes right? so what is their purpose

 

[Metanoia]

suppose if there is a compound with carboxylic acid and ketone group.. so I'll try to name as such both the functional groups are a part of the longest chain..? and if thats not possible, at least carboxylic acid should be .. right?

Moreover what's the use of the prefix??? for example ester prefix is ''oxycarbonyl'' and aldehyde's is OXO but we do not use these terms to name esters/aldehydes right? so what is their purpose

If there is a carboxylic acid and ketone group, the carboxylic acid is of a higher rank. The parent (longest) chain must contain carboxylic acid (and not necessary the ketone group).

Prefixes are used when there are more than 1 functional groups, I'll use alcohol to explain the idea of the prefix.

If alcohol is the highest ranked group, the molecule will be named as "-ol".

If alcohol is not the highest ranked group among the functional groups (e.g. alcohol and ketone), the prefix of alcohol (hydroxyl) would be used instead.

hydroxyl -ketone molecule


Additional point, you made mistake in naming the prefix of aldehyde as "oxo".
Prefix of aldehyde is formyl and prefix of ketones is oxo.
Having said that, it is unlikely that students are required to memorize the ranking to name complicated molecules.

 

[The Sarcastic Retard]

In the reaction of HCN with Carbonyl compounds, we use NaCN as a catalyst or as a source of CN- ions?

http://www.chemguide.co.uk/mechanisms/nucadd/hcntt.html

 

[Xylferion]

In the reaction of HCN with Carbonyl compounds, we use NaCN as a catalyst or as a source of CN- ions?

While making displayed formula, do we have to take care of making the right structure with the correct bond angles too? for example in J10/23Q5 part a, the structure given in the Marking scheme is absolutely perfect in terms of the bond angles etc but when I make displayed formulas generally I tend to just display all the bonds ( not caring about the bond angles)
So is my method acceptable?

CN- acts as the catalyst, NaCN is just there as a provider.

NaCN ----> Na + and CN-

 

[princess Anu]

is my cycle correct? (particularly the highlighted part) and do we need to balance it?

 

[qwertypoiu]

is my cycle correct? (particularly the highlighted part) and do we need to balance it?

It seems correct to me, as for balancing of the stuff in the box it's better to do it but it won't affect your answer.

 

[forest822]

Can anyone explain to me these few questions?

1. The density of ice is 1.00gcm-3. What is the volume of steam produced when 1.00cm3 of ice is heated to 323 degree celcius (596K) at a pressure of one atm (101 kPa) [ 1 mol of gas occupies 24.0dm3 at 25 degree celcius (298K) and one atm.
Ans: 2.67 dm3

2.Which of the following would behave most like an ideal gas at room temp?
Ans: Helium (Why Helium not Hydrogen?)

3. What are the assumptions of the kinetic theory of gases and hence of the ideal gas equation, PV= nRT?
Ans: molecules move without interacting with one another except for collisions ( Why does this statement mean?)

4. When a sample of gas is compressed at constant temp from 1500 kPa to 6000 kPa, its volume changes from 76.0cm3 to 20.5 cm3. Which statement are possible explanations for this behavior?
Wrong ans: The gas partially liquefies / Gas is absorbed on to the vessel walls ( Why)?

Thank You.!

 

[Jewel504]

Hey can someone pls explain the answer to question 5 may/june year 2012 paper 2 qp 21

 

[Studydayandnight]

Guys, I am struggling with this question!!!! :'(

It's May June 2014, 23 Question 1 (b) (v)

(v) Deduce the values of x, y and z in the equation in (iv)

PLEASE HELP!!!http://maxpapers.com/wp-content/uploads/2012/11/9701_s14_qp_23.pdf