If the atmospheric pressure at 30.0 km is 28.0 torr and the temperature is - 39.0 °c, what is the volume of the balloon when it bursts?

We from gas equation:

PV=mRT

Where:

P is pressure (1 torr = 0.013N/cm2)

V is the volume of the balloon

m is the mass of gas in the balloon (constant)

R is universal gas constant divided by mean molar wt of air (about 28 g/mol) T is thermodynamic temperature (T in Kelvin; T=273 + t (in deg C)

So, For given values in gas equation andassuming we have 1 gm of gas in the balloon, we get:

28 * V = 1 * R * (-39+273)

or, 28 * 0.013 * V = 1 * 28 * 324

or, V = 324 / 0.013 cm^3

or, V = 18000 cm^3