We need to find the molar quantity of benzene, and thus we simply perform the operation:
#"Mass"/"Molar mass of benzene"# to give an answer in moles, #=#
#(2.24*cancelg)/(6xx12.011*cancelg*mol^-1+6xx1.00794*cancelg*mol^-1)#
#=0.0287*mol#.
Note that this is dimensionally consistent, because, #1/("mol"^-1)=1/(1/"mol")="mol"#
So there are #0.0287*mol# of benzene #"molecules"#.
And since #1*mol-="Avogadro's number of molecules"# #=# #6.022xx10^23*mol^-1#
And #=0.0287*mol*"benzene molecules"xx6.022xx10^23*mol^-1="How many benzene molecules?"#
And #"how many atoms?"#, #=0.0287*molxx12*"atoms"*mol^-1xx6.022xx10^23*mol^-1="How many atoms?"#
Why did I need to multiply the molar quantity by #"12 atoms?"#
