x Turn on thread page Beta
 You are Here: Home

# AS Chemistry- helping each other out! watch

1. (Original post by C0balt)
the solution stays colourless.
All group 2 compound form white precipitate
Only transition metals form coloured ones (dichromate, permagnate have colours but they are transition metal anion)
Thank you! Do you know which transition metals would form a blue precipitate?
2. (Original post by prophetkid)
Thank you! Do you know which transition metals would form a blue precipitate?
Cu2+ ion is blue

Posted from TSR Mobile
3. How do I work out;

mass of MG(OH)2 that may have been used in the medicine.

Mass = molesxmr
mass = moles x 58.3

Info given is; hcl moles is 20.4 x 10^-3
The amount of acid which was used was 50cm^3 and concentration was 1moldm^3

(may need to work the hydroxide ions or something along them lines?)
4. (Original post by Uwaiss)
How do I work out;

mass of MG(OH)2 that may have been used in the medicine.

Mass = molesxmr
mass = moles x 58.3

Info given is; hcl moles is 20.4 x 10^-3
The amount of acid which was used was 50cm^3 and concentration was 1moldm^3

(may need to work the hydroxide ions or something along them lines?)
Write out the balanced chemical equation for the reaction and then you can work out the mole ratio

Posted from TSR Mobile
5. Hey!
Can you please tell me how do you do this?
It would be great help!
Thanks a lot

The answer is C btw but idk how!
Attached Images

6. (Original post by samb1234)
Write out the balanced chemical equation for the reaction and then you can work out the mole ratio

Posted from TSR Mobile
Mg(OH)2 + 2HCL -> MgCl2 + 2H20

2:1 ratio now what dude
7. (Original post by Uwaiss)
How do I work out;

mass of MG(OH)2 that may have been used in the medicine.

Mass = molesxmr
mass = moles x 58.3

Info given is; hcl moles is 20.4 x 10^-3
The amount of acid which was used was 50cm^3 and concentration was 1moldm^3

(may need to work the hydroxide ions or something along them lines?)
ratio 1:2 because
Mg(OH)2+2HCl -> H2O+MgCl2

So number of moles of Mg(OH)2 is half that of HCl

Multiply it by the Molar mass of Mg(OH)2 and that's the mass of Mg(OH)2
8. (Original post by C0balt)
ratio 1:2 because
Mg(OH)2+2HCl -> H2O+MgCl2

So number of moles of Mg(OH)2 is half that of HCl

Multiply it by the Molar mass of Mg(OH)2 and that's the mass of Mg(OH)2
and about that ion thing, it's a separate question
if you want the number of moles of OH- ions that is double the number of moles of Mg(OH)2 because there are 2 OH- in one Mg(OH)2
can any one else doing aqa confirm that this format is acceptable

a) X/n = 2.46728478
= 2.47 (3sf)
Part b depends on part a

b) m = (2.467...)(5)
= 12.33572814684 (not actual value)
=12.3 (3sf)
10. I do the aqa course and I was told to round the figure to the same SF as there are in the largest SF numbers given within the question if that helps
11. (Original post by GeorgiaW1122)
I do the aqa course and I was told to round the figure to the same SF as there are in the largest SF numbers given within the question if that helps
i understand that bit but when in the second part of the question it asks you to use the first answer , do you use the rounded answer or the unrounded answer
12. I'd use the ungrounded answer as it would signify that you are trying to keep your results as reliable and valid as possible
13. (Original post by chemphys)
i understand that bit but when in the second part of the question it asks you to use the first answer , do you use the rounded answer or the unrounded answer
I would do unrounded as it shows u are trying to be the most reliable and accurate that you can
14. (Original post by GeorgiaW1122)
I would do unrounded as it shows u are trying to be the most reliable and accurate that you can
ok thanks, thats what i have been doing for ages - however , how do you make it clear to the examiner that you are using the unrounded answer
do you just
put something like (0.201...) to show that you are using the whole thing not the rounded answer thanks

Also a friend of mine has suggested that if you carryb through with the full unrounded answer you lose marks as that was not you final answer for part (i) has anyone mentioned that to you thanks
15. When ever I have been given an equation to do that has multiple steps I have always used the unrounded numbers until the very end where I then round them to the amount of SF in the question and I've always came out with the correct answer

And you could use the ellipsis or you could round it to 3dp or the amount of SF in the given numbers of the question I've never done the ellipsis as it has never been accepted in a final answer but is has during the working out of the final answer
16. (Original post by khushboo1028)
Hey!
Can you please tell me how do you do this?
It would be great help!
Thanks a lot

The answer is C btw but idk how!
I have drawn them out for you! Sorry for the messiness
Edit: the one in the middle has one too many H

Posted from TSR Mobile
17. Does anyone have access to the June 2014 F321 & F322 papers? I would be very grateful!
18. Finally finished making notes all 117 pages of them

Posted from TSR Mobile
19. (Original post by chemphys)
ok thanks, thats what i have been doing for ages - however , how do you make it clear to the examiner that you are using the unrounded answer
do you just
put something like (0.201...) to show that you are using the whole thing not the rounded answer thanks

Also a friend of mine has suggested that if you carryb through with the full unrounded answer you lose marks as that was not you final answer for part (i) has anyone mentioned that to you thanks
I do physics with AQA but they allow using unrounded number for calculations at least for physics
And in my physics ISA my teacher made a note on my table that unrounded value was used for one of the columns in the table. I don't know about chemistry but I don't see why they should be different.

Note to others

just because I mentioned physics ISA DONT BOMBARD MY INBOX ABOUT IT. Your PM will immediately be reported if it's about ISA info trading

but any question UNrelated to physics ISA is WELCOME and I will try to help you as much as possible and as soon as possible if you PM or quote me

Posted from TSR Mobile
20. (Original post by samb1234)
Finally finished making notes all 117 pages of them

Posted from TSR Mobile
Geez, how long did that take?

Posted from TSR Mobile

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: July 24, 2017
Today on TSR

### Four things top students are doing

Over the Easter break

### Her parents made her dump me

Poll

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE