explanation: 1 mole of p2o5 (phosphorus pentoxide) with excess water gives 2 moles of phosphoric acid h3 po4. 2 moles of phosphoric acid in excess of ammonium hydroxide, produces 2 moles of (nh2) hpo4 salt (s) and hydrogen gas.
molecular weight of p2o5 : 2*31+ 16*5 = 142
molecular weight of (nh2) hpo4 : 14+3+31+64 = 112
100gms of nh2 hpo4 = 100/112 = 25/28 moles come from
=> 25/56 moles of p2 o5
=> 25/56 * 142 = 63.39 gms.
p2 o5 + 3 h2 o => 2 h3 po4
2 h3 po4 (aq) + 2 nh4 oh (aq) ==> 2(nh2) hpo4 (s)+3h2 (g)+ 2h2o
we know that in the final product, phosphorus is present only in (nh2)hpo4. it contains one atom of p. there are two atoms of p in p2o5. hence, we know easily that 1 mole of pentoxide gives (nh2)hpo4 (s) precipitate.
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can u share a pic of ur quesn
its not clear