We would use mixing rule here.
Let C = Concentration
V = Volume.
Mix 1 + Mix 2 = Final Mix.
C1V1 + C2V2 = CV
C1 = 35% = 0.35, V1 = Let it be x.
C2 = 68% = 0.68, V2 = (100 - x). Since total volume = 100 ml.
C = 47.21% = 0.4721, V = 100 ml.
Applying equation:
0.35* x + 0.68*(100- x) = 100*(0.4721).
0.35x + 68 - 0.68x = 47.21
0.35x - 0.68x = 47.21 - 68
-0.33x = -20.79. Divide both sides by - 0.33
x = -20.79/-0.33
x = 63.
Recall that x= 63, was for the 35% salinity.
For 68% salinity = (100-x) = (100 - 63) = 37 mL
Our answer is 37 mL for the 68% salinity.
