Answer to Question #23691 in Biochemistry for Chanel

Question

5. Assume the dissociation constant for NaCl is 1.8.
a) Show how you would prepare 400 ml of a 0.2% NaCl solution?
b) Would the above solution be hyper-, iso-, or hypo-osmotic to a 80mM NaCl solution?

Answer 1

The dissociation constant for NaCl cant be so high. If you don't make a mistake, and the dissociation constant is true 1.8, it will still not be enough information to calculate mass fraction or concentration in solution. If use value 1.8 as the density of the solution NaCl , instead the dissociation constants in question, the solution will be:
a) For preparation of 400 ml of 0.2% solution we need to calculate the mass of NaCl that we add to the water what is the solvent.
0.2%=0.002;
M=58.5 g/mol;
density of the solution = 1.8 g/ml =>
[NaCl]=0.002*(1.8/58.5)=0.000062 M = 0.062 mM =>
m/(M*V)=0.000062 M => m=0.0015 g.
b) Using concentration calculated above we can say the above solution would be hypo-osmotic.