Question

1. Suppose you have a 100-gram sample of each of the following compounds. Which sample contains the largest number of moles of compound?

chromium(III) chloride

ammonia

magnesium chloride

phosphoric acid

potassium chloride

nitrogen trioxide

methane

propane

lithium chlorate 2. How many molecules of ethanol (C2H5OH) (the alcohol in alcoholic beverages) are present in 571 mL of ethanol? The density of ethanol is 0.789 g/cm3. Express your answer numerically to three significant figures using e notation, so 1.23x1021 is entered as 1.23e21

Answer 1

no of moles of chromium(III) chloride    = W/G.M.Wt

                                                               = 100/158.36

                                                               = 0.63 moles

no of moles of NH3   = W/G.M.Wt

                                   = 100/17   = 5.88 moles

no of moles of MgCl2 = W/G.M.Wt

                                   = 100/95   = 1.05moles

no of moles of H3PO4   = W/G.M.Wt

                                      = 100/98 = 1.02 moles

no of moles of KCl   = W/G.M.Wt

                                 = 100/74.5   = 1.34moles

no of moles of N2O3   = W/G.M.Wt

                                     = 100/76   = 1.31 moles

no of moles of CH4 = W/G.M.Wt

                                 = 100/16 = 6.25 moles >>>>>>largest no of moles

no of moles of C3H8    = W/G.M.Wt

                                     = 100/44 = 2.27 moles

2.

mass of C2H5OH    = volume * density

                                = 571*0.789   = 450.52 g

no of molecules   =   W*6.023*10^23/G.M.Wt

                              = 450.52*6.023*10^23/56    = 4.84*10^23 molcules