Answer:
2.5 g
Explanation:
The partial coefficient (K) is the ratio of the solubility (S) of a solute in two different solvents. For the given problem:
K = Ssolvent/Swater
The solubility is the mass divided by the volume. If the fraction of the solute in water is called q, the fraction of it in the solvent is 1-q. Let's call m the initial mass of the solute, so, after the extraction:
mass at the solvent = (1-q)m
mass at water = qm
Ssolvent = (1-q)m/50
Swater = qm/80
8 = [(1-q)m/50]/qm/80
8 = 80*(1-q)/50q
400q = 80 - 80q
480q = 80
q = 0.167
The mass that remains at the water is:
0.167*15 = 2.5 g
