66.8 ml
Assuming that the pressure remains constant, we can use the ideal gas law which is
PV=nRT
where
P = pressure
V = volume
n = number of moles
R = Ideal gas constant
T = absolute temperature
Since in this problem we're keeping R, T, and P constant, we can eliminate them from consideration, so
V=n
which means that volume will be proportional to number of moles.
So we have the following ratio
2.451/36.7 = X/1
0.066784741 = X/1
0.066784741 = X
So the volume of the balloon will be 0.066784741 liters, or 66.784741 ml
Rounding to 3 significant figures gives 66.8 ml
