1. The problem statement, all variables and given/known data At an altitude of about 10 km, the temperature of the Earth’s atmosphere is roughly -50°C and the air pressure is around 16 kPa. (Assume ideal gas) How many kilograms of hydrogen gas (H2, molecular mass 2g/mol) should be put in a balloon to fill it to 2000 m3? What is the required mass of total ballast that the balloon will float at constant height (molecular mass of air 29 g/mol)? 2. Relevant equations PV = nRT 3. The attempt at a solution For 1. I used V = (P*A*N)/(R*T) = ( 2g/mol * 16000 Pa * 2000m^2 ) / (8.314 * 223K) = 34.51 Kg I don't know if it's correct way to do it or not For the second part I have no idea how to even start.