IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: AS-Girl on November 24, 2010, 11:21:35 am

Title: chemistry people..come in!!
Post by: AS-Girl on November 24, 2010, 11:21:35 am: hi people

I got these 2 questions which i couldn't solve...the most important thing i need to know is the way of getting the answer!! so if anyone knows i would appreciate the help

I need the explanation of question 11 and 12!
scaned working out would be preferable hehe

Thanks in advance
Title: Re: chemistry people..come in!!
Post by: Deadly_king on November 24, 2010, 02:20:40 pm: First you should write the equation showing the solubility of the salt.

In the first case it's Pb₂C₂O₄ -----> Pb²⁺ + C₂O₄^2-

Now you can write the K_sp

Ks_p = [Pb²⁺][C₂O₄^2-]

Since mole ratio of the two ions formed is 1:1, we can take it to be $x$ : $x$

So K_sp = $x$ ² = 8.5 x 10^-9

Now you just have to find the value of $x$ . ;)

I'll let you try the 2nd one yourself. If you can't do tell me and i'll try to be clearer :D
Title: Re: chemistry people..come in!!
Post by: AS-Girl on November 24, 2010, 03:59:11 pm: Thanks deadly king :D

regarding the second question...i followed the same steps
so Ksp= Ag2CrO4------>2 Ag+ + CrO4 (-2)

ratio moles is 2:1
so what happens next? im stuck here?!!
Title: Re: chemistry people..come in!!
Post by: Amelia on November 24, 2010, 04:37:59 pm: Ag₂CrO₄ ---> 2Ag⁺ + CrO₄^2-

Solubility of CrO₄ = 3.2x10^-5
Solubility of Ag⁺ = 2 x 3.2x10^-5

Ksp = [Ag⁺]² [CrO₄]
Ksp = (2 x 3.2x10^-5)² (3.2x10^-5)
Calculate and you get the answer. :)
Title: Re: chemistry people..come in!!
Post by: AS-Girl on November 24, 2010, 05:03:46 pm: Thanks Amelia :D :D

idea is cleared..if i got any other question..i'll surely post it here!!

Thanks again :)
Title: Re: chemistry people..come in!!
Post by: Amelia on November 24, 2010, 05:16:37 pm: Quote from: AS-Girl on November 24, 2010, 05:03:46 pm
Thanks Amelia :D :D

idea is cleared..if i got any other question..i'll surely post it here!!

Thanks again :)

You are welcome. ;D
Title: Re: chemistry people..come in!!
Post by: Deadly_king on November 25, 2010, 04:29:10 am: Quote from: Amelia on November 24, 2010, 04:37:59 pm
Ag₂CrO₄ ---> 2Ag⁺ + CrO₄^2-

Solubility of CrO₄ = 3.2x10^-5
Solubility of Ag⁺ = 2 x 3.2x10^-5

Ksp = [Ag⁺]² [CrO₄]
Ksp = (2 x 3.2x10^-5)² (3.2x10^-5)
Calculate and you get the answer. :)

Very well done my li'l princess :D

+rep
Title: Re: chemistry people..come in!!
Post by: Amelia on November 25, 2010, 06:55:06 am: Quote from: Deadly_king on November 25, 2010, 04:29:10 am
Very well done my li'l princess :D

+rep

Thanks, daddy. :P :D