What mass of phosphorus is contained in a #15.5*g# mass of #P_2O_5#?

1 Answer
Mar 10, 2017

Answer:

#"Mass of phosphorus"~=7*g#.

Explanation:

We need (i) to assess the molar quantity of #P_4O_10# (which of course is the same as #P_2O_5#, and which formula we can use without loss of generality).

#"Moles of"# #P_4O_10# #=# #(15.5*g)/(283.89*g*mol^-1)=0.0546*mol#.

Now in one mole of #P_4O_10#, CLEARLY there are 4 moles of phosphorus. So (ii) we need to multiply the given molar quantity by #4xx30.9737*g*mol^-1#, where #30.9737*g*mol^-1# is the atomic mass of phosphorus.

#"Mass of phosphorus"# #=# #0.0546*molxx4xx30.9737*g*mol^-1#

#~=7*g#.