can you show us how you tried to solve it? (with balanced equation?) we can look at your steps and help to find where to put you on the right track.
Since SrF2 is a slightly soluble salt, some of it actually dissolves and is in solution. That is where the Ksp comes in. A dissociation equation is needed to go along with the Ksp equation. There might be a section of solubility and equilibrium in your textbook.
No balanced equation was given in the problem so formulated it myself. I got this equation:
2NaF + Sr(NO3)2 ---> 2Na(NO3)2 + SrF2
These is what I did to find the sodium ion concentration:
The number of moles of Na+ present in the original 75 mL solution is
75 mL x 1 L x 0.06 mol NaF x 1 mol Na
1000 mL 1 L 1 mol NaF
= 4.5 x 10-3 Na+.
The total volume after combining the two solutions is 100 mL. The concentration of Na+ in the 100 mL volume is
[Na+] = 4.5 x 10-3 mol x 1000 mL
100 mL 1 L
[Na+] = 0.045.
Using the same logic I got the the concentration of NO3-
= 0.076. However, if I will further apply this to the Sr2+ and F-, I can't arrive at the correct answer.
just a bit of organization....
1. Calculate INITIAL concentrations of Na+ and NO3-
No balanced equation was given in the problem so formulated it myself. I got this equation:
2NaF + Sr(NO3)2 ---> 2Na(NO3)2 + SrF2
These is what I did to find the sodium ion concentration:
The number of moles of Na+ present in the original 75 mL solution is
75 mL x 1 L x 0.06 mol NaF x 1 mol Na
1000 mL 1 L 1 mol NaF
= 4.5 x 10-3 Na+.
The total volume after combining the two solutions is 100 mL. The concentration of Na+ in the 100 mL volume is
[Na+] = 4.5 x 10-3 mol x 1000 mL
100 mL 1 L
[Na+] = 0.045.
good
[NO3-]= 2 x 25 x 0.15 /100 = 0.075 !
2. Calculate INITIAL concentrations of Sr2+ and F- like above BUT then...
Start with a limiting reagent approach to find out what is left in the solution.
3. then
Since SrF2 is a slightly soluble salt, some of it actually dissolves and is in solution. That is where the Ksp comes in. A dissociation equation is needed to go along with the Ksp equation. There might be a section of solubility and equilibrium in your textbook.
This is a problem with common ion effect (an excess of strontium cation)
quite a bit of work here...
4. Finally correct answers are..
(Concentrations of the species should be Na+ = 0.045, F- = 1.1 x 10-4.
NO3- should be 0.075,
Sr2+ should be 0.015
if you neglect ionic strenght.