• We need your support!

    We are currently struggling to cover the operational costs of Xtremepapers, as a result we might have to shut this website down. Please donate if we have helped you and help make a difference in other students' lives!
    Click here to Donate Now (View Announcement)

Physics, Chemistry and Biology: Post your doubts here!

Messages
103
Reaction score
21
Points
18
guys the last question in p62 chemistry is always about planning an investigation and is difficult for me so guys some good tips u can give me

thnx in advance
 
Messages
1,824
Reaction score
5,326
Points
523
umm...... so I am having a problem in answering the questions where we have to write which is more concentrated based on the volumes of the substances in chem paper 6
How do we know that the substance was supposed to be more concentrated because more amount volume is used or the substance was less concentrated because more volume was used?
Can anybody plz help me out? Thnx............... :)
 
Messages
273
Reaction score
83
Points
38
umm...... so I am having a problem in answering the questions where we have to write which is more concentrated based on the volumes of the substances in chem paper 6
How do we know that the substance was supposed to be more concentrated because more amount volume is used or the substance was less concentrated because more volume was used?
Can anybody plz help me out? Thnx............... :)

There are two scenarios for this:-

1) Check this paper first(MJ2011 QP61 Q4 e(iii)):- https://drive.google.com/folderview...sp=drive_web&tid=0BzumkDfi9230ajBJb1BVUl8xODg

So in this case the student is pouring solution(for which concentration is being checked) of potassium manganate(VII) from the beaker. Thus, the lesser the volume required for the colour to change, the more concentrated it is.

2)https://drive.google.com/folderview...drive_web&tid=0BzumkDfi9230ajBJb1BVUl8xODg(MJ 2008 QP6 Q4 e(iii))

So in this case the solution for which concentration is being checked is not poured, the known volume is already in the flask. Thus, whatever is being poured, in this case potassium manganate(VII), has to be in larger volume.

So basically you just have to look if the solution checked for concentration(i.e. A and B) has a known volume or not. If it does not, then the one with the smaller difference is more concentrated. If it does have a known volume, then one with larger difference is more concentrated.

Good luck for your exams
 
Last edited:
Messages
456
Reaction score
280
Points
73
So in the marking scheme they say:
"Heat for specified time,record temp, greatest temp rise better fuel"
I wrote :
"Heat till boiling point of 100°C, record time taken, less time taken better fuel"
Is this acceptable?Screenshot_2015-05-11-16-56-24.png
 
Messages
47
Reaction score
21
Points
18
Guys for paper 0620/62/O/N/12 Question 5 (j) the marking scheme says any transition metal but copper, why not copper?
 
Messages
4,988
Reaction score
23,955
Points
523
So in the marking scheme they say:
"Heat for specified time,record temp, greatest temp rise better fuel"
I wrote :
"Heat till boiling point of 100°C, record time taken, less time taken better fuel"
Is this acceptable?View attachment 53484
Nope.Why would you want to boil it till 100°C?
Do you know you are just burning the fuel?
The fuel when burned gives energy, that heats the water,so the fuel that shows more rise in temperature is a better fuel.

(You can take a look at this if you like :)
https://www.xtremepapers.com/commun...t-your-doubts-here.11053/page-420#post-916013)
 
Messages
456
Reaction score
280
Points
73
To distinguish between water and ethanol:
Test : Add magnesium
Water: Bubbles of Hydrogen
Ethanol: No reaction
Acceptable?
 
Messages
95
Reaction score
35
Points
28
To distinguish between water and ethanol:
Test : Add magnesium
Water: Bubbles of Hydrogen
Ethanol: No reaction
Acceptable?
No ethanol reacts with magnesium as magnesium is more reactive than the Hydrogen so displaces it.
Ethanol + Magnesium ---> Magnesium Ethoxide + Hydrogen (Not sure of spelling though)
A better test would be B.P Ethanol more volatile than water
Chemical test would be test pH using "pH meter" and water would have neutral and ethanol more alkaline. Write meter as it would be able to detect slight alkaline solution as well
 
Messages
192
Reaction score
31
Points
38
No ethanol reacts with magnesium as magnesium is more reactive than the Hydrogen so displaces it.
Ethanol + Magnesium ---> Magnesium Ethoxide + Hydrogen (Not sure of spelling though)
A better test would be B.P Ethanol more volatile than water
Chemical test would be test pH using "pH meter" and water would have neutral and ethanol more alkaline. Write meter as it would be able to detect slight alkaline solution as well
ph meter not possible as both are neutral so cant distinguish but for ethanol and ethanoic acid ph meter is possible!
 
Top