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

1 Answer
anor277
Jul 4, 2017

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........"#

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