pts) A 25.0 mL sample of water from the lake was acidified and treated with excess sodium molybdate, leading to the formation of 12 -molybdophosphoric acid (12-MPA):

+ 24 H+ =====-> H3PMO12040

+ 24Nat +

12 H20

HsPO4 + 12 NazMoO4

The 12-MPA was separated from the excess sodium molybdate by extraction with two successive 10.0 mL portions of iso-amyl alcohol. When the combined extract was aspirated into the flame of an atomic absorption spectrometer set-up for measuring molybdenum, an absorbance of 0.662 was obtained. The absorbance of a 5.00- ppm Mo standard in the same volume of iso-amyl alcohol was 0.203.Calculate the ppm PO43 in the sample.