What is the name of the compound with 77.3% silver, 7.4% phosphorous and 15.3% oxygen?

1 Answer
anor277
Jan 8, 2017

#"Silver phosphate"#, #Ag_3PO_4#.

Explanation:

As with all of these problems, we assume there are #100*g# of compound, and proceeed on this basis to derive the empirical formula by calculating the individual molar quantites. And given #100*g# of stuff, there are:

#"Moles of silver"=(77.3*g)/(107.9*g*mol^-1)=0.716*mol#

#"Moles of phosphorus"=(7.4*g)/(31.00*g*mol^-1)=0.239*mol#

#"Moles of oxygen"=(15.3*g)/(16.00*g*mol^-1)=0.956*mol#

For each element we have divided by the atomic mass of the given element to give a molar quantity of that element.

We now divide thru by the SMALLEST molar quantity, that of phosphorus:

#"Equivs of silver"# #=# #(0.716*mol)/(0.239*mol)# #=# #3#

#"Equivs of phosphorus"# #=# #(0.239*mol)/(0.239*mol)# #=# #1#

#"Equivs of oxygen"# #=# #(0.956*mol)/(0.239*mol)# #=# #4#

And thus the empirical formula, the simplest whole number ratio representing equivalent quantities in a species is:

#Ag_3PO_4#

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