Question #6b701

1 Answer
Jul 10, 2015

The usual composition of phosphate rock is about 30 % #"P"_2"O"_5#, which corresponds to 66 % of #"Ca"_3("PO"_4)_2#.

Explanation:

The composition of phosphate rock (PR) is usually reported as % #"P"_2"O"_5#.

The composition varies from 26 % to 35 %, depending on the source.

Let's assume an average of 30 % #"P"_2"O"_5# or 30 g #"P"_2"O"_5# per 100 g of PR.

We can convert this to % #"Ca"_3("PO"_4)_2# as follows.

#30 cancel("g P₂O₅") × (1 cancel("mol P₂O₅"))/(141.94 cancel("g P₂O₅")) × (1 cancel("mol Ca₃(PO₄)₂"))/(1 cancel("mol P₂O₅")) × ("310.18 g Ca"_3("PO"_4)_2)/(1 cancel("mol Ca₃(PO₄)₂")) = "66 g Ca"_3("PO"_4)_2#

So, if the #"P"_2"O"_5# is present as #"Ca"_3("PO"_4)_2#, 30 % #"P"_2"O"_5# corresponds to 66 % #"Ca"_3("PO"_4)_2#.