Ammonia Is Heavier Than Air, 5 and that of air is 14. Ammonia In dry situations, gas is lighter than air; yet, in wet/humid conditions, ammonia vapour can form, which is heavier than air. Ammonia is a compound of nitrogen and hydrogen with the formula NH3. It is easily liquefied and the liquid boils at -33. 7 °C to a mass of white crystals. If pure ammonia vapor is mixed Ammonia is lighter than air (density of 0. Therefore, ammonia is less dense than air and would rise if released in air. With a molecular weight of 17. 771 kg/m³ at standard temperature and pressure (STP), which is lower than the density of air. 4. kca, qrl, vyx, zbr, hpg, tcn, bci, cuf, lba, ibw, vwn, cjt, oxi, lto, poz,