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# Edexcel IGCSE Chemistry 18th May/June 2017 Thread watch

1. (Original post by gpit6903)
What did people get for the mass question.... i got 9kg
Yeh I did too that's right as long as you put kg after
2. (Original post by Glazmann)
same- I was completely not confident in my answers, unlike biology. My friend said she found the chemistry easier than the biology, but for me, it was the other way around!
unrelated but omg I love your profile picture!
3. (Original post by gpit6903)
What did people get for the mass question.... i got 9kg

It was 9kg
4. Any unofficial mark schemes? Can someone make a google docs
5. (Original post by 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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I don't get why you added them. 250cm3 was the volume of the gas in the syringe. 90 was the reading on the syringe, not the initial volume. Correct me if I'm wrong, but that's how I remember it. If I do remember it correctly, then you're not supposed to mix the two values up.
6. (Original post by JMR2017)
For the one where you had to find the x of h2o, I did not really understand it and I wrote 8 as an answer.
Next to the equation I wrote the mass, molar mass and moles for each, but do you think I would get any marks for this?
I think the molar masses of MgSO4 and H2O were given in the question anyway. So you divided the constant mass of dehydrated MgSO4 remaining (which was 8.4) by the molar mass (120) which gave 0.07.

The mass of water driven off (8.82g) was divided by 18 (molar mass of water) to give 0.49.

Ratio is 1:7 (as 0.49 divided by 0.07 = 7) so X = 7
7. (Original post by uvuvwevwevwe)
I don't get why you added them. 250cm3 was the volume of the gas in the syringe. 90 was the reading on the syringe, not the initial volume. Correct me if I'm wrong, but that's how I remember it. If I do remember it correctly, then you're not supposed to mix the two values up.
UGH this question really annoyed me - I got 28% but everyone is saying that its wrong - besides the amount that IS actually in air is 21% so 20.5 seems more likely
8. (Original post by gpit6903)
What did people get for the mass question.... i got 9kg

Same!

What did you guys get for the reason water was added to iron powder?
9. (Original post by uvuvwevwevwe)
I don't get why you added them. 250cm3 was the volume of the gas in the syringe. 90 was the reading on the syringe, not the initial volume. Correct me if I'm wrong, but that's how I remember it. If I do remember it correctly, then you're not supposed to mix the two values up.
I'm pretty sure 250cm3 was the volume of the flask... and there was already 90cm3 in the syringe. So you need to add them together.

I made the same mistake and didn't add them up so I got 28% as well. But we know oxygen is around 21%. I'm sure there will be a method mark for seeing 70cm3 used though.

There may even be a method mark for getting 28% as you've calculated it the correct way. If it was a 3 mark question you'll only get all 3 for 20.5% or 20.6%. You don't even need to show any working if the final answer is correct to get full marks.
10. (Original post by Darwinion)
I think the molar masses of MgSO4 and H2O were given in the question anyway. So you divided the constant mass of dehydrated MgSO4 remaining (which was 8.4) by the molar mass (120) which gave 0.07.

The mass of water driven off (8.82g) was divided by 18 (molar mass of water) to give 0.49.

Ratio is 1:7 (as 0.49 divided by 0.07 = 7) so X = 7
Do I lose any mark for not writing the un-rounded ratio?
11. what did you guys put for the last question?
12. (Original post by comu)
what did you guys put for the last question?
I put that the higher temperature would provide a higher kinetic energy hence, each particle will have more chance of having enough activation energy for the reaction to start. Not 100% sure tho
13. (Original post by comu)
what did you guys put for the last question?
I said something about the particles spread out in random motion due to having more energy, increasing the (surface) area for the reaction to take place but I feel like that's completely wrong !!
14. I got 28% as did 70/250 x100
15. (Original post by comu)
what did you guys put for the last question?
16. For the last question, I think I put something about liquids expanding on heat - more molecules.

I thought the glass rod was a thermometer. DOH!
17. (Original post by BerylTheBird)
I put that the higher temperature would provide a higher kinetic energy hence, each particle will have more chance of having enough activation energy for the reaction to start. Not 100% sure tho
I said exactly the same... after crossing out that the teacher must have crushed the solid more to create a larger surface area. I literally put that in the final 2 minutes.
18. What does everyone think they got realistically?

For me, I think I got about 65%, maybe 70.

Got 9kg for water too.
19. (Original post by BerylTheBird)
Do I lose any mark for not writing the un-rounded ratio?
Don't think so. If you put 7 as final answer you score full marks anyway even without showing any working. You always do on the marks schemes I've seen.
20. what did people get for the compounds that went through the filter paper? I got water and magnesium sulfate but other people are saying that sulfuric acid went through the filter paper.

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