AQA GCSE Chemistry C2/C3 May 15th 2014

Calculate the percentage yield if 9.0g MgSO4 was made from 4.0g MgO.

I knew how to do this before, but I've spent 30 minutes trying to work this out? CHESWDCKJNEWLksmdc.m sdkj
The answer is 75%. Please explain. -_-

Reply 21

interstitial

18

Original post by rm_27

Calculate the percentage yield if 9.0g MgSO4 was made from 4.0g MgO.

I knew how to do this before, but I've spent 30 minutes trying to work this out? CHESWDCKJNEWLksmdc.m sdkj
The answer is 75%. Please explain. -_-

What's the reaction equation?

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Reply 22

rm_27

11

Original post by majmuh24

What's the reaction equation?

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It's not given. I think they assume we should know it.

Reply 23

interstitial

18

Original post by rm_27

It's not given. I think they assume we should know it.

I assume it's MgO + SO3 ==> MgSO4 then (was there something to do with acid rain?)

1 mol. Mg ==> 1 mol. MgSO4

RMM magnesium is 24
RMM oxygen is 32
RMM sulfur is 16

Using this, we get that

56g MgO ==> 168g MgSO4

Dividing by 14 gives

4g MgO ==> 12g MgSO4

And the problem is easy from there :smile:

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Reply 24

chronicmusic

OP

6

Original post by rm_27

It's not given. I think they assume we should know it.

Sorry but I don't know >.<

Reply 25

chronicmusic

OP

6

Original post by Silver-wind

Come at me brah

Please give me any tips you have

Reply 26

Delirious97

Oxygen is 16...sulfur 32 :P

Reply 27

Confusedchild124

okay so basically the relative atomic masses first
oxygen =16
sulfur=32
magnesium=24

so mgo---> mgS04

mgo=24+16=40
mgso4 = 24=16=(16x3)=120

so its 40:120
which can be cancelled to 4:12
so 12g of mgso4 should be produced
actual/theoretical X 100 to get the percentage yield right
so 9/12 = 0.75x100 = 75% not that hard theyre just trying to be confusing!

(edited 9 years ago)

Reply 28

Nath98

4

Anyone got any thoughts on what the 6 marker will be on C2? Based on previous years etc?

Reply 29

Kevin Paul Beale

Original post by chronicmusic

Please give me any tips you have

Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!

Reply 30

hi-zen-berg

12

Original post by Kevin Paul Beale

Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!

and whats that then :tongue:

Reply 31

mohiniangel

Do you guys think anything on nano particles will come up? Or precipitation reactions? Titration was last year, but could it be repeated?

Reply 32

chronicmusic

OP

6

Original post by Kevin Paul Beale

Got a feeling about whats going to come up in the exam, it came to me and the more I think about it the more it makes sence!

Have you got the Folens revision guide? It's really good for downloading powerpoints and claiming they are your own work that took you 12 hours!

Reply 33

chronicmusic

OP

6

Predicted 6 markers for C2:

I believe there will be 2 six markers, the first on nanoscience (uses and what nanoparticles are) and the other on polymers (platics, thermosoftening/setting, exothermic/endothermic). Only one will be a QWC though so you'll need about 4/5 points each

Reply 34

voxdock

6

Original post by chronicmusic

Predicted 6 markers for C2:

I believe there will be 2 six markers, the first on nanoscience (uses and what nanoparticles are) and the other on polymers (platics, thermosoftening/setting, exothermic/endothermic). Only one will be a QWC though so you'll need about 4/5 points each

nanoscience has loads of points, polymers I can think of maybe 2/3 for each

Reply 35

chronicmusic

OP

6

Original post by voxdock

nanoscience has loads of points, polymers I can think of maybe 2/3 for each

Yeah true, would you mind listing your points to help me/other people out?

Reply 36

kkomde

Can someone please explain to me how to make insoluble salts? I tried CGP and my-gcsescience but I still can't understand. :confused:

Reply 37

voxdock

6

Original post by chronicmusic

Yeah true, would you mind listing your points to help me/other people out?

nanoparticles-1-100nm in length, inc fullerenes
nano science: fullerenes
huge SA:vol so industrial catalysts
nanomedicine-absorbtion by body
cosmetics
buildings
strong covalent bonds, so strong
conductrors-computer parts
sun cream

Reply 38

ssalmaa

My teacher has a strong feeeling that electrolysis is going to be on the c2 exam for the 6 marks...im really worried an unprepared for this exam!

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Reply 39

chronicmusic

OP

6

Original post by kkomde

Can someone please explain to me how to make insoluble salts? I tried CGP and my-gcsescience but I still can't understand. :confused:

I will use silver chloride as an example. Silver chloride is insoluble. You need a soluble silver salt and a soluble chloride salt to make it. Silver nitrate and sodium chloride are both soluble. When you mix their solutions together, you make soluble sodium nitrate and insoluble silver chloride:

•

silver nitrate + sodium chloride → sodium nitrate + silver chloride

•

AgNO₃(aq) + NaCl(aq) → NaNO₃(aq) +AgCl(s)

The silver chloride appears as tiny particles suspended in the reaction mixture - it forms a precipitate. The precipitate can be filtered, washed with water on the filter paper, and then dried in an oven.
Remember: if you want to make an insoluble salt XY, mixing X nitrate with sodium Y will always work. In the example above, X is silver and Y is chloride.

AQA GCSE Chemistry C2/C3 May 15th 2014

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