Chemistry: Post your doubts here!

[Konstantino Nikolas]

Can someone please tell me where 244 came from?

So, I doubt that the marking scheme cites 244 kJ/mol since I think it would be 242 kJ/mol as per the data booklet and that is the enthalpy change of atomisation of Cl2 molecule which at have to take into consideration during the calculation.

Yes, the bond energy of Cl2 is 242 in the 2016 specimen data booklet. The value must have been given as 244 in the data booklet of that particular year.

 

[Lola_sweet]

So, I doubt that the marking scheme cites 244 kJ/mol since I think it would be 242 kJ/mol as per the data booklet and that is the enthalpy change of atomisation of Cl2 molecule which you have to take into consideration during the calculation.

Yes, the bond energy of Cl2 is 242 in the 2016 specimen data booklet. The value must have been given as 244 in the data booklet of that particular year.

why do we need bond energy though in calculating this?
the book didnt use it :/

 

[Catherine_1]

why do we need bond energy though in calculating this?
the book didnt use it :/

So see since you are calculating the lattice energy we take into consideration the respective enthalpy change of atomisation and electron affinity/ionisation energies(depending on whether it is a metal or non-metal). In this case, 1 mol of Cl2 molecule will form Cl atoms which will further form 1 mole of Cl- ions.Therefore, we are taking bond energy basically, Enthalpy change of atomisation, to convert chlorine molecules into atoms.

 

[Lola_sweet]

So see since you are calculating the lattice energy we take into consideration the respective enthalpy change of atomisation and electron affinity/ionisation energies(depending on whether it is a metal or non-metal). In this case, 1 mol of Cl2 molecule will form Cl atoms which will further form 1 mole of Cl- ions.Therefore, we are taking bond energy basically, Enthalpy change of atomisation, to convert chlorine molecules into atoms.

Ohhhh Thank You so much

 

[Catherine_1]

Ohhhh Thank You so much

You're welcome.

 

[Xaptor16]

Can someone please help me with paper 5 its literally my nightmare... I solved O/N/09 and as the markscheme isn't very helpful I have no way of marking it myself, I wanna know how to construct an experiment t and everything... Could someone solve question 1d please?

 

[Konstantino Nikolas]

Can someone please help me with paper 5 its literally my nightmare... I solved O/N/09 and as the markscheme isn't very helpful I have no way of marking it myself, I wanna know how to construct an experiment t and everything... Could someone solve question 1d please?

http://cieoandalevelnotes.blogspot.in/2015/05/chemistry-level-paper-5-p5-solved-past.html Follow the link in that website ... it has solved chemistry P5 ... might help you out.

 

[Lola_sweet]

can someone tell me the difference between substituted amide and unsubstituted?

 

[Konstantino Nikolas]

can someone tell me the difference between substituted amide and unsubstituted?

 

[a_wiserME!!]

how is 81Br+ one species and 79Br+ another??

 

[Konstantino Nikolas]

View attachment 59299

how is 81Br+ one species and 79Br+ another??

cuz they have 2 different masses?

jk ... got no idea of this topic yet

 

[FranticAmaze]

View attachment 59299

how is 81Br+ one species and 79Br+ another??

I did same ppr.... Din know how to do this..hav to ask sir

 

[a_wiserME!!]

I did same ppr.... Din know how to do this..hav to ask sir

I'm assuming it to be this way...Br2 has one Br+ and Br- and one combination is where both Brs are +/-?? just ask him if this is what it is..

 

[a_wiserME!!]

the table 2nd and 3rd row ?? why is a=1 in the 2nd??

 

[a_wiserME!!]

the balancing of the equation in c(ii) pls with the working

 

[a_wiserME!!]

 

[a_wiserME!!]

the ratio is 9:6:1 but how does that come about?

 

[a_wiserME!!]

part (iii) pls

 

[FranticAmaze]

View attachment 59305

the ratio is 9:6:1 but how does that come about?

View attachment 59306

part (iii) pls

which ppr??

 

[a_wiserME!!]

which ppr??

O/N/09

and the second one M/J/09