IGCSE Chemistry Revision Guide | According to syllabus

[wooowooowoo]

How did you do in paper 1/3?
Shouldn't worry too much, 10 marks in paper 5 ( if it's out of 40) is only 5% of total grade, and last year p3 was easier than this but grade threshold was 70-75%(EDIT: For an A* that is) so don't worry!

anyone do the physics practical 52? so freaking lengthy and our school is just stupid. my glass slab was not shaped exactly like a rectangle it was tilting at one edge so i got my refractive indexes different and they didnt even setup the force experiment at the start. im sure no one loses more than 5 marks in these practicals but i know im gonna lose atleast 10

Exactly, I was so bored.. I ended up calculating the marks.
30 marks loss in p3
5 marks loss in p1
5 marks loss in p6
Will end up as an A* (i hope it's not wrong)

 

[israa33]

HOW WAS THE PHYSICS AND LITERATURE PAPERS TODAY????????????
i loved both of them ...
they were realllllly easy....

 

[kanishk]

Exactly, I was so bored.. I ended up calculating the marks.
30 marks loss in p3
5 marks loss in p1
5 marks loss in p6
Will end up as an A* (i hope it's not wrong)

hey why does the grade threshold say out of 200 marks when its like 160 marks? do they take out percentages of each paper or something? and were you able to finish the practical in time?what do you think the minimum marks to get A* will be out of 200?

 

[wooowooowoo]

hey why does the grade threshold say out of 200 marks when its like 160 marks? do they take out percentages of each paper or something? and were you able to finish the practical in time?what do you think the minimum marks to get A* will be out of 200?

Yes, I finished on time (well 15 minutes before time)
As far as I know, they first calculate the percentage out of 160 and then convert it to 200.
Last year it was 150/200 which is around 120/160 (so a mistake of 40 marks in all paper combined would still give you an A*, I guess? Anyone with valid source to prove it?)
This year it should be around the same as even last year people found their paper to be relatively tough. Don't expect it to go VERY low.

 

[IGSCE.Geek.]

Yes, I finished on time (well 15 minutes before time)
As far as I know, they first calculate the percentage out of 160 and then convert it to 200.
Last year it was 150/200 which is around 120/160 (so a mistake of 40 marks in all paper combined would still give you an A*, I guess? Anyone with valid source to prove it?)
This year it should be around the same as even last year people found their paper to be relatively tough. Don't expect it to go VERY low.

is this variant 2? anyway what does oxides of nitrogen do? and how does he catalytic converter help (please describe in details!)

 

[wooowooowoo]

is this variant 2? anyway what does oxides of nitrogen do? and how does he catalytic converter help (please describe in details!)

Oops yeah I should have specified (Yes I was talking about Variant 2)

Well Oxides of Nitrogen are formed when oxygen reacts with Nitrogen. Engines in the cars are very hot and they give nitrogen and oxygen (present in the air) and opportunity to get to know each other better (react), they react at high temperature to form Nitrogen Monoxide.
The monoxide then leaves the car and reacts with more oxygen to form Nitrogen Dioxide. It might mix with water to form Nitric Acid rain and get evaporated to give out acid rain.

Catalytic Converters:
Car fuels contain carbon; so carbon monoxide gas is released by cars as waste fumes, as well as nitrogen oxides.
These are pollutant gases. To prevent these gases from polluting air, a device called catalytic converter is fitted at
the end of the exhaust. This device contains a catalyst which catalyses the reaction between these two gases
producing two harmless gases, nitrogen and carbon dioxide:


The catalyst of the device works best at temperature around 200°C.

^ from the notes

 

[kanishk]

Yes, I finished on time (well 15 minutes before time)
As far as I know, they first calculate the percentage out of 160 and then convert it to 200.
Last year it was 150/200 which is around 120/160 (so a mistake of 40 marks in all paper combined would still give you an A*, I guess? Anyone with valid source to prove it?)
This year it should be around the same as even last year people found their paper to be relatively tough. Don't expect it to go VERY low.

remember the glass slab one where you had to find the refractive index twice? will they cut marks if they are not equal? and i mean not equal by alot i was getting 1.38 in one and 1.6 in the other....but all the distances were accurate and is on the ray trace sheet.what do you think how many marks would i lose

 

[Lost_Life]

 

[wooowooowoo]

Pardon ?

remember the glass slab one where you had to find the refractive index twice? will they cut marks if they are not equal? and i mean not equal by alot i was getting 1.38 in one and 1.6 in the other....but all the distances were accurate and is on the ray trace sheet.what do you think how many marks would i lose

Refractive index twice? Really? When was that ?

 

[kanishk]

Pardon ?

Refractive index twice? Really? When was that ?

dude which variant did you do? they said repeat the steps c to j with incident ray 25 degrees to the left of the normal and you had to find the index again using a and b

 

[IGSCE.Geek.]

another thing.... do fats have a functional group and if so, WHAT THE HELL IS IT!!! thank you for you appreciation

 

[wooowooowoo]

another thing.... do fats have a functional group and if so, WHAT THE HELL IS IT!!! thank you for you appreciation

Fat itself doesn't have but it breaks down to Fatty Acids and Glycerol
Acid and Alcohol.
Anyone with better theory?

EDIT : Fats are esters, made by reaction of acid and alcohol - Lol it was right in front of my eyes, yet I missed it. It's not made by polymerisation

 

[IGSCE.Geek.]

K. i hate ionic equations!!!!

 

[IGSCE.Geek.]

is gasoline part of petroleum gases?

 

[IGSCE.Geek.]

im gunna do terribly!!!!!!!!!!

 

[kanishk]

someone link me the hardest chemistry paper ever till now
and help me with this question
c) A 5.00 g sample of impure lead(II) nitrate was heated. The volume of oxygen formed was
0.16dm3 measured at r.t.p. The impurities did not decompose.
Calculate the percentage of lead(II) nitrate in the sample.
2Pb(NO3)2 → 2PbO + 4NO2 + O2
Number of moles of O2 formed = .......................................
Number of moles of Pb(NO3)2 in the sample = .......................................
Mass of one mole of Pb(NO3)2 = 331 g
Mass of lead(II) nitrate in the sample = ....................................... g
Percentage of lead(II) nitrate in sample = .....................................
tell me how you got each too please

 

[IGSCE.Geek.]

someone link me the hardest chemistry paper ever till now
and help me with this question
c) A 5.00 g sample of impure lead(II) nitrate was heated. The volume of oxygen formed was
0.16dm3 measured at r.t.p. The impurities did not decompose.
Calculate the percentage of lead(II) nitrate in the sample.
2Pb(NO3)2 → 2PbO + 4NO2 + O2
Number of moles of O2 formed = .......................................
Number of moles of Pb(NO3)2 in the sample = .......................................
Mass of one mole of Pb(NO3)2 = 331 g
Mass of lead(II) nitrate in the sample = ....................................... g
Percentage of lead(II) nitrate in sample = .....................................
tell me how you got each too please

is it finding the mass of a pure lead nitrate?

 

[IGSCE.Geek.]

someone link me the hardest chemistry paper ever till now
and help me with this question
c) A 5.00 g sample of impure lead(II) nitrate was heated. The volume of oxygen formed was
0.16dm3 measured at r.t.p. The impurities did not decompose.
Calculate the percentage of lead(II) nitrate in the sample.
2Pb(NO3)2 → 2PbO + 4NO2 + O2
Number of moles of O2 formed = .......................................
Number of moles of Pb(NO3)2 in the sample = .......................................
Mass of one mole of Pb(NO3)2 = 331 g
Mass of lead(II) nitrate in the sample = ....................................... g
Percentage of lead(II) nitrate in sample = .....................................
tell me how you got each too please

1. n=v/24:; n=0.16/24=0.006mol
2.n=m/M; 5/331=0.015mol
3.......? is it pure lead nitrate????

 

[kanishk]

d

1. n=v/24:; n=0.16/24=0.006mol
2.n=m/M; 5/331=0.015mol
3.......? is it pure lead nitrate????

ude no clue this is how the question was....the answer to 2 is 0.013 and 3 is 4.4g i dont know how they got it.....and i did the same thing you did in 2 but its wrong

 

[Lost_Life]

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! what is meant by a reductant!!!!!!!!!!!!!!!!!!!!!!