Physics, Chemistry and Biology: Post your doubts here!

DANISH182

DANISH182

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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
 
sj0007

sj0007

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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............... :)
 
X

XxChampXx

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sj0007 said:
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............... :)
Click to expand...

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
 
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Saad the Paki

Saad the Paki

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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
 
UsamaFTW

UsamaFTW

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Guys for paper 0620/62/O/N/12 Question 5 (j) the marking scheme says any transition metal but copper, why not copper?
 
M

My Name

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Saad the Paki said:
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
Click to expand...
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)
 
Saad the Paki

Saad the Paki

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To distinguish between water and ethanol:
Test : Add magnesium
Water: Bubbles of Hydrogen
Ethanol: No reaction
Acceptable?
 
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