Physics, Chemistry and Biology: Post your doubts here!

[Adeen Atif]

yea i got that notice too...but i think the paper will start at 3
they r just calling us early because there r some 600 or so candidates and its hard for them to manage

Really,
But aren't there almost 600 candidates every time?

 

[Osman Kaleem]

Really,
But aren't there almost 600 candidates every time?

are u from riyadh

 

[Adeen Atif]

are u from riyadh

Yes

 

[Osman Kaleem]

Yes

me too

 

[Ayesha Asif333]

Really,
But aren't there almost 600 candidates every time?

 

[Osman Kaleem]

Has anyone got answers of feb mar 2017 chem paper 4

 

[dannyboy123]

Hydrolysis of a polymer gave a compound with the following composition by mass: C, 34.61%;
H, 3.85%; O, 61.54%.

whats the answer???

 

[Osman Kaleem]

Hydrolysis of a polymer gave a compound with the following composition by mass: C, 34.61%;
H, 3.85%; O, 61.54%.

whats the answer???

C3H4O4

 

[Osman Kaleem]

I think we must discuss answers of feb mar chem paper 4 to make sure of them

 

[Va_nes_sa]

does anyone have the feb/mar 2017 papers please?

 

[Osman Kaleem]

i begin for Q1
ai) A
ii) B and C
iii) D
iv) A
v) A
vi) Carbon dioxide and water
bi) lubricating fraction and bitumen
ii) refinery gas
iii) refinery gas
iv) kerosene
v) boiling of petroleum

 

[Adeen Atif]

i begin for Q1
ai) A
ii) B and C
iii) D
iv) A
v) A
vi) Carbon dioxide and water
bi) lubricating fraction and bitumen
ii) refinery gas
iii) refinery gas
iv) kerosene
v) boiling of petroleum

Im just solving them,after solving we will discuss

 

[Adeen Atif]

View attachment 62153

Ok,Thanks

 

[Adeen Atif]

does anyone have the feb/mar 2017 papers please?

Search on facebook and youll find an IGCSE chemistry question answers group there.
Some of the students have shared the paper.

 

[Osman Kaleem]

Btw the internet transactions have been hacked

 

[Osman Kaleem]

Please be careful

 

[Osman Kaleem]

Q2a) filtration wash with excess water then dry between tissue papers

 

[Osman Kaleem]

bi) -2
ii) 2Ag+ + Cr2O7-2
c) turns blue ammonia is produced
di) ammonium dichromate has more Mr then silver nitrate slower rate of diffusion and red solid was silver dichromate
ii) less time taken as more energy so more rate of diffusion
ei) breaking down of substancesdue to heat *
ii) (NH4)2Cr2O7 = Cr2O3 + N2 + 4H2O

 

[Adeen Atif]

Q2a) filtration wash with excess water then dry between tissue papers

The answer for 2a is: Filter the solution
Wash with distilled water
Dry in Oven

 

[Adeen Atif]

bi) -2
ii) 2Ag+ + Cr2O7-2
c) turns blue ammonia is produced
di) ammonium dichromate has more Mr then silver nitrate slower rate of diffusion and red solid was silver dichromate
ii) less time taken as more energy so more rate of diffusion
ei) breaking down of substancesdue to heat *
ii) (NH4)2Cr2O7 = Cr2O3 + N2 + 4H2O

di) is: The solids are dissolved
Then solid silver nitrate diffuses faster than solid ammonium dichromate due to lower Mr.
Then these two salts react together to form silver dichromate(the red solid) at point S