GCHEM Q # 61 ADA.....please help :)

[whale86]

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In which of the following solutions would CaF2 be LEAST soluble?

1- .01M CaCl2
2- .02M CaCl2
3- .01M NaF
4- .02M NaF
5- .02M NaCl

an explanation would be great as well...thanks 🙂

 

[sfoksn]

Um I think it may be choice 4..

CaF2 dissociates into Ca2+ and 2F-.

F- concentration would increase faster, of course, due to higher coefficients.

I think if you put it in 0.2M of NaF solution, the F- concentration would hit the saturation level the fastest.

Correct me if I am wrong

 

[whale86]

Um I think it may be choice 4..

CaF2 dissociates into Ca2+ and 2F-.

F- concentration would increase faster, of course, due to higher coefficients.

I think if you put it in 0.2M of NaF solution, the F- concentration would hit the saturation level the fastest.

Correct me if I am wrong

CaF2? Im confused.....where did you get the CaF2 from?

 

[sfoksn]

In which of the following solutions would CaF2 be LEAST soluble?

1- .01M CaCl2
2- .02M CaCl2
3- .01M NaF
4- .02M NaF
5- .02M NaCl

an explanation would be great as well...thanks 🙂

Aren't you dissolving the CaF2?

 

[UndergradGuy7]

CaF2? Im confused.....where did you get the CaF2 from?

The question asks in what solution will CaF2 be least soluble? So the least soluble solution is one that already has some Ca or some F in it.
The equation is CaF2 -> Ca^2+ + 2F^-
So Ksp = (Ca^2+)*(F^-)^2
Notice F- is squared so it has a higher impact.

Choice 5 has none of them so CaF2 will dissociate in it the best.

1- .01M CaCl2 It has 0.1 M Ca
2- .02M CaCl2 It has 0.2 M Ca
3- .01M NaF It has 0.1 M F
4- .02M NaF It has 0.2 M F

So choice 4 has F-. Above we said F- is squared so it has a higher impact on the solubility. choice 4 is 0.2 M F- so it will have the highest impact on solubility. choice 4 is the least soluble.

 

[sfoksn]

Typos, just to make sure the OP doesnt' get confused

The question asks in what solution will CaF2 be least soluble? So the least soluble solution is one that already has some Ca or some F in it.
The equation is CaF2 -> Ca^2+ + 2F^-
So Ksp = (Ca^2+)*(F^-)^2
Notice F- is squared so it has a higher impact.

Choice 5 has none of them so CaF2 will dissociate in it the best.

1- .01M CaCl2 It has 0.1 M Ca <-- 0.01M
2- .02M CaCl2 It has 0.2 M Ca <-- 0.02M
3- .01M NaF It has 0.1 M F <-- 0.01M
4- .02M NaF It has 0.2 M F <--0.02M

So choice 4 has F-. Above we said F- is squared so it has a higher impact on the solubility. choice 4 is 0.2 M F- so it will have the highest impact on solubility. choice 4 is the least soluble.

 

[whale86]

sfoksn- lol yes we are dissolving in CaF2 sorry I had a BLAH moment 😀


thankss guys for your responses i appreciate it!!