can someone help me with this question jan 2010
A chemical company has a waste tank of volume 25 000 dm3. The tank is full ofphosphoric acid (H3PO4) solution formed by adding some unwanted phosphorus(V)oxide to water in the tank.A 25.0 cm3 sample of this solution required 21.2 cm3 of 0.500 mol dm–3 sodiumhydroxide solution for complete reaction.Calculate the mass, in kg, of phosphorus(V) oxide that must have been added to thewater in the waste tank.
i worked out the moles of NaOH which was 0.0109
and then using the equation P4O10+ 6H20> 4H3PO4 i thought wouldve given me the moles of P4O10 when divided by 4 but it says 0.0109/3 even with the reaction H3PO4+ 12NaOH> 4h3po4 it would be wrong have i got the formula wrong?