Question

What mass and volume of `"25% orthophosphoric acid"` is required for a `1.0*mol*L^-1` solution of `H_3PO_4(aq)`?

Answer 1

You need to quote the `"density"`, `rho`, `"of 25% orthophosphoric acid"`.

Explanation:

And http://pubs.acs.org/doi/abs/10.1021/ie50546a062 quotes `rho=1.17*g*mL^-1`. This value should have been quoted with the question.

And so we can work out the concentration, by considering just a `"litre volume"`.

We need `((97.99*g)/(97.99*g*mol^-1))/(1.0*L " of solution")`.

And so we need `97.99*g` with respect to `H_3PO_4`.

`=(97.99*g)/(25%xx1.17*g*mL^-1)=335.0*1/(1/(mL))=335.0*mL`

And so we take a `335.0*mL` volume of `25%(w/w)` `H_3PO_4`, and dilute it up to a ONE LITRE volume. The order of addition is important, because `"if you SPIT in acid it spits back........"`