Unit 3B Chemistry :) How was the exams? Comment here :P

[ithinkforit]

i messed up in the last questn... btw what were ur answers to the calculations?

like which calculations.....i dun really rmmbr

 

[Hailstorm94]

Some questions I remember:
1) Why do you add the Iodine in small quantities?
2)Why use anhydrous calcium sulphate?
3) What is the 9th step?
4) Why is this question not suitable for large-scale manufacturing? (last question)

oh also
Why observations would you see when you add NaI to ---- don't rem?

1. u sure the question is structured right? if so its due to the reaction being very exothermic... 2) its a drying agent and it needs to be dry so to able to absorb the water/aq solution... i only wrote the first half :-/ wrote absorb part but crossed out telling myself dont try to be smart 3) (re)distillation 4) wide range of answers my topper friend said re phos is expensive and the 80% yeild is low... i went with the safety approach... HCl gas produced which is toxic... i wrote acidic so its a hazard... sily explanation also butan 1 ol is flammable so could explode and lastly the reaction is very/highly exothermic which would back the butan 1 ol explosion statement... last one is nai and h2so4 u will see purple vapour HI and black solid I2... my friend wrote steamy fumes instead of iodine i think thatll be in ignore since all 3 na halides produce it so its nothing special...

 

[Hailstorm94]

two ways to do that question 2x0.5/46.5 x100 gets u 2.15% so 2.2%... or 47.5-46.5/46.5 x 100

 

[Manasa]

like which calculations.....i dun really rmmbr

number 2

 

[Manasa]

1. u sure the question is structured right? if so its due to the reaction being very exothermic... 2) its a drying agent and it needs to be dry so to able to absorb the water/aq solution... i only wrote the first half :-/ wrote absorb part but crossed out telling myself dont try to be smart 3) (re)distillation 4) wide range of answers my topper friend said re phos is expensive and the 80% yeild is low... i went with the safety approach... HCl gas produced which is toxic... i wrote acidic so its a hazard... sily explanation also butan 1 ol is flammable so could explode and lastly the reaction is very/highly exothermic which would back the butan 1 ol explosion statement... last one is nai and h2so4 u will see purple vapour HI and black solid I2... my friend wrote steamy fumes instead of iodine i think thatll be in ignore since all 3 na halides produce it so its nothing special...

hey do u remembr how many marks its worth? all qustn 3?

 

[Hailstorm94]

hey do u remembr how many marks its worth? all qustn 3?

19

 

[Sara5396]

I hated the paper really much! :'(

 

[anan123456789]

if i lose 15 will it be a B or a C

 

[Mufaddal]

in calculating the energy of the reaction were we supposed to use 50 or 55?

 

[bloom princeton]

Do they care about the spelling? If yes.. Im finished :'(

well if the spelling gives a whole meaning of a completely existent different word then maybe yes..if not like u said the vigorous spelling was wrong by only adding a 'u' then dont wrryyy...this info is written in the markscheme so u can chill and focus on the upcoming units the worth 40% each this unit only worths 20%

 

[bloom princeton]

if i lose 15 will it be a B or a C

dont wrryy it depends on the curve i.e how hard was the paper for the overall candidates but judging 15 marks that would be a B when u compare it to january 2013 examination boundary which was helll easier than this...so chillllll

 

[nadee_W]

For question 1 - I wrote something about the reaction being very exothermic/volatile
2 - I think it should have been something about the drying agent but I wrote some fake stuff (water/needs further distillation)
3-

3- redistillation
4- i wrote some nonsense for that..not sure about my answer..

 

[aniekan]

I do have mistakes but it was better than bio 3b!

Obviously

 

[lateefa3]

Dude..........wasnt it Calcium Carbonate............??????

It was Calcium carbonate xD

 

[qstar.inc]

though the exam was better than prediction, but still "I hate you, Chemistry"

 

[qstar.inc]

it was absent so the observation should have been no change but I didn't see it and wrote white ppt insoluble

same mistake

 

[qstar.inc]

It was Calcium carbonate xD

Calcium Carbonate was Y, right?

 

[cardude456]

Calcium Carbonate was Y, right?

Yh

 

[qstar.inc]

i dont remember seeing anything which said sulfate was absent !

on the first question after the flame test, the second one's last column said "Sulphur was absent"

 

[qstar.inc]

i wrote no ppt formed colorless solution
abt the compound i wrote C3H8O

is that the empirical formula, right?