Problem 32E

A molecule with the formula AB3 has a trigonal planar geometry. How many electron groups are

on the central atom?

Solution :Step 1 : Given, Mass of gas in 2-L flask = 4.8g. Pressure of gas in 2-L flask = X xtm. Mass of gas in 3-L flask = 0.36g. Pressure of gas in 3-L flask = 0.1 X atm.We should find if two gases have the same molar mass, if not which contains the gas of highermolar mass. Consider ideal gas equation : PV = nRT ‘n’ , number of moles can be calculated as mass divided by molar mass. Hence we canrewrite the ideal gas equation as : Mass PV = Molar mass ×RTUsing the above equation, we can find the molar mass of the gases. Mass×RT Molar mass = PV