Edexcel IGCSE Chemistry 18th May/June 2017 Thread

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My answer was that you should use the glass rod to feel if crystals have been formed - wasn't confident with the answer though

I think it's because the drops of near saturated solution on the glass rod cool down much more quickly as you lift them out so it becomes totally saturated and crystallises out. You know it's ready to leave to dry then.

(edited 6 years ago)

Reply 61

MarimbaMofo

I got 28%, I thiiiink it was right, but I was worried about how far it was from 21% as well :/

Reply 62

Cunningham99

I got 21% because I divided by the volume of the conical flask which it gave as 250 cm3 and the volume initially in the syringe which was 90 cm3...... Anyone else do this and get like 20.5%??

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Reply 63

MNOV

Original post by hiiya to

What did people get for the percentage of oxygen in air?? Cos my answer was 28% which wasn't very near 21% :/

I got that

Reply 64

Emm22

Original post by Cunningham99

Yea I got 21% as well because I divided 70 by the gas in the conical flask and in the glass tube and the volume of gas in during at start so i added 250 + 90. So I did (70/340) times 100 which is like 21.5

Reply 65

Darwinion

Original post by Cunningham99

I got 28% as well. I can't remember the figures exactly. I used the 250cm3 in the flask but wasn't the 90cm3 in the syringe minus the 20cm3 remaining. I'm sure I used a figure of 70 somewhere.

But if you add the 250cm3 to the 90 you get 340cm3 and 70/340 x 100 does indeed come to 20.5%.

If that's the case I got that wrong. :/

(edited 6 years ago)

Reply 66

Simselene

Original post by hiiya to

What did people get for the percentage of oxygen in air?? Cos my answer was 28% which wasn't very near 21% :/

sameee!

Reply 67

georgetbarber

Original post by Cunningham99

Yeah this is right

Reply 68

not_XIX_forever

To test if the solution will crystalise :smile:

Original post by MontyZuma

How did everyone find the exam? I thought it went pretty well. Especially compared to Biology!

One question though...why do you put the glass rod in the solution!?

Reply 69

Darwinion

I think if you stated that 70cm3 of air was used you'll get a method mark. Something like "M1 70 seen". Hope so anyway :tongue:

Reply 70

not_XIX_forever

I got 7 too :wink:

Original post by MarimbaMofo

I got 7, i think :smile:

Reply 71

not_XIX_forever

Ugh so annoying! I put 28 too. :frown:

How many marks was that question anyway?

Original post by Darwinion

I think if you stated that 70cm3 of air was used you'll get a method mark. Something like "M1 70 seen". Hope so anyway :tongue:

Reply 72

Emm22

What answers did you guys get for the equilibrium questions?

Reply 73

Darwinion

Original post by Emm22

What answers did you guys get for the equilibrium questions?

I put that the pressure difference had no effect as 2 molecules were present each side of the equation. I can't remember the other bits.

Reply 74

gpit6903

Original post by archibald300

I got 7 too :wink:

me too but it was through ratios 0.049 into the number gave me 7

Reply 75

ITSJDOG

I got 22.2% and I think it was a 3 mark question. This chemistry paper started off fairly easy but started to get pretty hard towards the second half in my opinion. I found the moles question pretty hard😬

Reply 76

gpit6903

Original post by Darwinion

I put that the pressure difference had no effect as 2 molecules were present each side of the equation. I can't remember the other bits.

Yeah I got that too, there was 2 moles on each side. I said that increasing the pressure increased the rate of reaction though.

It was exothermic right?