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Topic: precipitate:confusion on set up...  (Read 2511 times)

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Offline dds*90210

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precipitate:confusion on set up...
« on: July 20, 2010, 02:16:44 AM »
A 10mL solution is .10M with respect to both calcium nitrate and magnesium nitrate. Which of the following will be true if 0.10M NaF solution
is added by drops until ppt forms?
ksp = 4 x 10-11 for CaF2 and 6.4 x 10-9 for MgF2

Answer choices:
A) ppt will be CaF2 only
B) ppt will be MgF2
C) ppt will have both as ppt
D) ppt will have Ca(NO3)2 and MgF2
E) ppt will have CaF2 and Mg(NO3)2


i started off with Ca + 2NO3 --> CaNO3
                       0        0                           0.10M
                       +x      +2x                           -x
but i think my setup is wrong cuz i did this through and my answeer was wrong.. can anyone show me the correct steps???

Offline AWK

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Re: precipitate:confusion on set up...
« Reply #1 on: July 20, 2010, 02:52:01 AM »
Quote
i started off with Ca + 2NO3 --> CaNO3
Ca2+ + 2F- --> CaF2(s)
AWK

Offline Jorriss

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Re: precipitate:confusion on set up...
« Reply #2 on: July 20, 2010, 06:27:06 PM »
Based on the Ksp's, what do you think will precipitate first?

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