What is known as a "Photochemical smog"? Discuss its formation mechanism. Air consists of three gases, namely, nitrogen, oxygen and Composition of nitrogen, oxygen and the argon are 75%, 20% and 5%, respectively. Molecular weights (in g/mol) of nitrogen, oxygen and ar 28, 32 and 40, respectively. Estimate the average molecular weight of air in g/l. Assume temperature and pressure to be 25C and 1 atmo Take value of universal gas constant as 0.08206 L.atm/mol.K [2+3+2=7]