Answer
Assuming the perfect osmosis across the semipermeable membrane at equilibrium, the volume inside the balloon will be at 0.5 L.
Work Step by Step
We may consider the $M_{1}$$V_{1}$ = $M_{2}$$V_{2}$ formula to determine the expected volume of the solution inside the balloon at equilibrium through osmosis.
Given:
Concentration of solution (some solute) where balloon is filled, $M_{1}$ = 0.2 M
Initial volume of solution in the balloon, $V_{1}$ = 0.25 L
Concentration of solution (some solute) where balloon is submerged, $M_{2}$ = 0.1 M
Calculate the expected volume of the solution inside the balloon at equilibrium, $V_{2}$ = ?
$M_{1}$$V_{1}$ = $M_{2}$$V_{2}$
(0.2 M)(0.25 L) = (0.1 M)($V_{2}$)
By substitution,
$V_{2}$=$\frac{(0.2 M)(0.25 L)}{(0.1 M)}$, Cancelling out the concentration, M
$V_{2}$= 0.5 L
