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Chemistry M/J 2015 Paper 52

PlutoHuman

PlutoHuman

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Less than 24 hours left! Can someone please share some last minute revision tips and tricks?
 
PlutoHuman

PlutoHuman

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If someone has some goood last minute revison notes or stuff like that please post here!
 
B

Bba321

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What are construction lines?
Please help don't know hat will happen tomorrow
 
Omar Haider

Omar Haider

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PlutoHuman said:
http://maxpapers.com/wp-content/uploads/2012/11/9701_w14_qp_52.pdf
Can someone do question 2 (e,f) please?
Click to expand...
The technique used to do this question is actually very different from others. For the first part, you have to find the pKa. This can be done using your graph. Remember, the pKa of the acid is equal to the pH at the half-neutralisation point. In other words, look at the volume where the pH rises rapidly, half this volume and look at the corresponding pH. This is your pKa. Now just convert this into Ka and you've done the first part. (Try this out and you'll get the right answer).

For the second part, use the pH to find concentration, that is 10^pH which will give you [H+] concentration. To find the concentration of HA, the equation used should be Ka = [H+]^2/[HA]. Since you've found [H+] and and you have Ka, you can now solve this part.
 
PlutoHuman

PlutoHuman

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nighthawk said:
Hey guys. Did anyone solve the winter 2014 paper 52 question 2 (e.f) ?

PlutoHuman what value did you get for the pH?
Click to expand...
i got 4.0
Omar Haider said:
The technique used to do this question is actually very different from others. For the first part, you have to find the pKa. This can be done using your graph. Remember, the pKa of the acid is equal to the pH at the half-neutralisation point. In other words, look at the volume where the pH rises rapidly, half this volume and look at the corresponding pH. This is your pKa. Now just convert this into Ka and you've done the first part. (Try this out and you'll get the right answer).

For the second part, use the pH to find concentration, that is 10^pH which will give you [H+] concentration. To find the concentration of HA, the equation used should be Ka = [H+]^2/[HA]. Since you've found [H+] and and you have Ka, you can now solve this part.
Click to expand...
the marking scheme has no answer for this. it just shows the working without any numbers......
 
Mayisha M

Mayisha M

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Omar Haider said:
The technique used to do this question is actually very different from others. For the first part, you have to find the pKa. This can be done using your graph. Remember, the pKa of the acid is equal to the pH at the half-neutralisation point. In other words, look at the volume where the pH rises rapidly, half this volume and look at the corresponding pH. This is your pKa. Now just convert this into Ka and you've done the first part. (Try this out and you'll get the right answer).

For the second part, use the pH to find concentration, that is 10^pH which will give you [H+] concentration. To find the concentration of HA, the equation used should be Ka = [H+]^2/[HA]. Since you've found [H+] and and you have Ka, you can now solve this part.
Click to expand...

Btw, thanks for this. You are a lifesaver man :)
 
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