How many molecules are in 75.0 g of diphosphorus pentoxide #P_2O_5#?

1 Answer
Mar 2, 2016

Answer:

We need to (i) calculate the molar quantity of phosphorus pentoxide, and (ii) convert the number of moles into a NUMBER.

Explanation:

Molar quantity #=# #"Mass"/"Molar Mass"# #=# # (75.0*cancelg)/(141.94*cancelg*mol^-1)# #=# #0.528# #mol#. #P_2O_5# has, of course, a molar mass of #141.94*g#. (Of course, the molecule is actually #P_4O_10#, but it does not really matter for this treatment.)

Now it is a fact that #1# #mol# of stuff contains #6.022xx10^23# individual items of that stuff.

So, #0.528# #mol# #xx# #6.022xx10^23*mol^-1# #=# #???# #"individual "P_2O_5" units"#. How many moles of phosphorus atom are in such a quantity; how many oxygen atoms?