Compounds Containing Nitrogen

Paragraph for next two questions
A trinitro compound, 1,3,5-tris-(4-nitrophenyl) benzene, on complete reaction with an excess of Sn∕HCl gives a major product, which on treatment with an excess of NaNO2∕HCl at 0∘C 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 474gmol−1 and between compounds P and S is 172.5gmol−1.