-90n =Molecular massEmpirical massMolecular formula of the compound is C2H204.= 2.45PRACTICE PROBLEMS1. Calculate the (a) empirical formula, and (b) molecular formula of a compound having the following percentage composition:Sodium 42.1%, phosphorus 18.9% and oxygen = 39.%. Given that the molecular mass of the compound is 164.(Na = 23, P = 31 and O = 16][Ans: (a) Na3PO, (b) Na3PO4]2. Urea is a very important nitrogenous fertiliser and has the molecular formula NH CONH2. Calculate the percentage ofnitrogen in urea.[Ans: 46.67%]3. A hydride of nitrogen contains 87.5% by mass of nitrogen. Determine its empirical formula.[Ans: NH2]4. 0.24 g sample of a compound of oxygen and boron was found by analysis to contain 0.096 g of boron and 0.144 g ofoxygen. Calculate the percentage composition of the compound by mass.[Ans: Boron = 40%; Oxygen 60%]5. Calculate the percentage of oxygen in K2Cr2O7. [K = 39, Cr = 52 and 0 = 16][Ans: 38.09%]6. Calculate, correct to one decimal point, the percentage of platinum in ammonium chloroplatinate ((NH4)2PtCl.).[Pt = 195, N = 14, H = 1 and Cl = 35.5][Ans: 43.9%]7. Calculate the empirical formula of a compound having the following percentage composition: K = 47.9%, Be = 5.5% andF = 46.6% by mass. [Be = 9, F = 19 and K = 39][Ans: K,BeF]8. A metal M forms a volatile chloride containing 65.5% chlorine. If the density of the chloride relative to hydrogen, i.e., VDis 162.5, find the molecular formula of the chloride. [M = 56 and Cl = 35.5).[Ans: M2016]9. In an experiment, 6.21 g of lead combines with 4.26 g of chlorine. What is the empirical formula of the chloride of leadmetal? [Pb = 207 and Cl = 35.5](Ans: Pbcla10. An organic compound with vapour density 94 contains C = 12.67%, H = 2.1% and Br = 85.11%. Find its molecular formula(C = 12, H = 1 and Br = 80][Ans: C2H4Br2)​