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
The total volume after combining the two solutions is 100 mL. The concentration of Na+
in the 100 mL volume is
] = 4.5 x 10-3 mol
x 1000 mL
100 mL 1 L
] = 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+
, I can't arrive at the correct answer.