Edexcel IGCSE Chemistry 18th May/June 2017 Thread

Reply 100

sportygal517

9

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

Reply 101

MarimbaMofo

7

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!

Reply 102

Harrrrryyyyyyy

4

Original post by gpit6903

What did people get for the mass question.... i got 9kg

It was 9kg

Reply 103

famileh

1

Any unofficial mark schemes? Can someone make a google docs

Reply 104

2959674

7

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%??

Posted from TSR Mobile

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.

Reply 105

Darwinion

12

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

Reply 106

sydxwood

8

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 :frown:

Reply 107

Lechatn0ir

14

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?

Reply 108

Darwinion

12

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.

(edited 6 years ago)

Reply 109

BerylTheBird

5

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?

Reply 110

comu

6

what did you guys put for the last question?

Reply 111

BerylTheBird

5

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

Reply 112

sydxwood

8

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 !!

Reply 113

Hlwilson2000

I got 28% as did 70/250 x100

Reply 114

Hlwilson2000

Original post by comu

what did you guys put for the last question?

What was this question on?

Reply 115

username3150658

15

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!

(edited 6 years ago)

Reply 116

Darwinion

12

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.

Reply 117

username3150658

15

What does everyone think they got realistically?

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

Got 9kg for water too.

Reply 118

Darwinion

12

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.

Reply 119

weirdperson7878

1

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.

Edexcel IGCSE Chemistry 18th May/June 2017 Thread

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