NaCl solution
 

i was wondering if any of you could help me figure out how much distilled water should be added to 5g of NaCl so that it completely dissolves. Thanks

I'm pretty confident I got it right, but no guarantees.
I had some problems finding out the solubility product for NaCl, one site told me that it is ~36 (mol/l)² (at 25 C), so that's what I'm using. It might be completely wrong though.

Because we want the solution to be saturated: Q = Ksp.
Q = c(Na+)c(Cl-) ; Ksp = 36

(n(Na+) / V(H2O)) * (n(Cl-) / V(H2O)) = 36 (mol/l)²
<=> (n(Na+)n(Cl-)) / (V(H2O)²) = 36 (mol/l)²
(NaCl -> Na+ + Cl-, so n(NaCl) = n(Na+) = n(Cl-))
<=> n(NaCl)² / (V(H2O)²) = 36 (mol/l)²
<=> n(NaCl) / V(H2O) = 6 mol/l
<=> V(H2O) = n(NaCl) / 6 mol/l

So we get V(H2O) = (5g/(22.99g/mol+35.45g/mol))/6 (mol/l) = 0.0855578371 l ~ 0.09 l

Hope this helps.

Thanks that helps me out a lot. And 25(c) is about the temp which im going to be working in, so im pretty sure u got it right, ill just check it over to make sure it makes sense before i use it. Thanks