Estimate the volume of a hydrogen filled balloon that can lift 24 kg load in air?

Question

Using the chemical symbols, what kind of disaster can be made from sulphur, hydrogen, iodine, phosphorous, tungsten, rhenium, carbon and potassium?

Answer 1

About 24 m3

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Air density = about 1.2 kg/m3.
Air molar mass = about 29,
Hydrogen molar mass = 2,
Hydrogen density is 2/29 *1.2 kg/m3 = ~0.1 kg/m3
The difference is about 1.1 kg/m3. Knock off a little for the mass of the envelope and rigging lines and it is down to 1 kg per m3.
24 m3 is approximate volume required to lift 24 kg load.