A trinitro compound, 1,3,5-tris-(4-nitrophenyl)benzene, on complete reaction with an excess of Sn/HCI gives a major product, which on treatment with an excess of NaNO2/HCI at 0C provides P as the product. P, upon treatment with excess of H2O at room temperature, gives the product Q. Bromination of Q in aqueous medium furnishes the product R. The compound P upon treatment with an excess of phenol under basic conditions gives the product S. The molar mass difference between compounds Q and R is 474 g mol-1 and between compounds P and S is 172.5 g mol-1. 17. The total number of carbon atoms and heteroatoms present in one molecule of S is [Use: Molar mass (in g mol-1): H = 1, C = 12, N = 14, O = 16, Br = 80, CI = 35.5 Atoms other than C and H are considered as heteroatoms]