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Chemistry: Post your doubts here!

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NinjaInPyjamas

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Haya Ahmed said:
Ohh Thanks ! ^_^ .. btw could You help me in Question 3 and 7 of the same paper please ? :)

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Chemistry (9701)/9701_w10_qp_12.pdf
Click to expand...

I'm sorry, I don't know how to explain q3.

q7 we know it to be constant temp. that's why we use the formula P x V

initial P x V = final P x V
So it should be flask X + flask Y = final pressure x volume
(P x V of X) +(P x V of Y) = P x V final
(5 x 12000) + (10 x 6000) = 15 x P
thus P = 8000 Pa = 8 kPa so answer is A
 
Haya Ahmed

Haya Ahmed

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NinjaInPyjamas said:
I'm sorry, I don't know how to explain q3.

q7 we know it to be constant temp. that's why we use the formula P x V

initial P x V = final P x V
So it should be flask X + flask Y = final pressure x volume
(P x V of X) +(P x V of Y) = P x V final
(5 x 12000) + (10 x 6000) = 15 x P
thus P = 8000 Pa = 8 kPa so answer is A
Click to expand...
okay now question 26 :p .. hope I'm not disturbing you
 
AbbbbY

AbbbbY

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sara kamal said:
i asked for part b, thanks for the reply though :)
Click to expand...
pH = pKa + lg([salt]/[acid]) (or pH = pKa - lg([acid]/[salt]) )
5.5 = -lg(1.79 × 10^-5) + lg([Sa]/[A])
5.5 - 4.75 = lg([Sa]/[A])
lg([Sa]/[A]) = 0.75
[Sa]/[A] = 10^0.75
[Sa]/[A]= 5.62
S = 5.62A
A+S = 100
100-A=5.62A
A = 15.1 = 15
So S = 85.

Acid = 15, Salt = 85. Is this the answer?


Edit: Somehow [ S ] wasn't being posted without the gaps so I just changed it to Sa.
 
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