Question

Question #6b701

Answer 1

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`.