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