In H_(3)PO_(4), which of the following is true

1.	In H_(3)PO_(4), which of the following is true
Answer» `K_(a)=K_(a_(1))xxK_(a_(2))xxK_(a_(3))` `K_(a_(1))ltK_(a_(2))ltK_(a_(3))` `K_(a_(1))gtK_(a_(2))ltK_(a_(3))` `K_(a_(1))=K_(a_(2))=K_(a_(3))` SOLUTION :`H_(3)PO_(4)hArrH^(+)+H_(2)PO_(4)^(-)Ka_(1)=([H^(+)][H_(2)PO_(4)^(-)])/([H_(3)PO_(4)])""...(i)` `h_(2)PO_(4)^(-)hArrH^(+)+HPO_(4)^(2-)K_(a_(2))=([H^(+)][HPO_(4)^(-2)])/([H_(2)PO_(4)^(-)])""...(ii)` `HPO_(4)^(2-)hArrH^(+)+PO_(4)^(3-)K_(a_(3))=([H^(+)][HPO_(4)^(2-)])/([HPO_(4)^(2-)])""...(iii)` `H_(3)PO_(4)hArr3H^(+)+P_(4)^(3-)K_(a)=([H^(+)]^(3)[PO_(4)^(3-)])/([H_(3)PO_(4)])""...(iv)` Multiplying (i),(ii), (ii) and equate with (iv) `K_(a)=K_(AQ)xxK_(a_(2))xxK_(a_(3)),therefore(a)` is correct `1^(st)` acid dissociation constant is highest because dissociation is maximum in FIRST step, less in `2^(nd)` step and MINIMUM in `3^(rd)` step because it is difficult for a negatively changed ion tolose `H_(+)` ion. `K_(a_(1))gtK_(a_(2))gtK_(a_(3)), therefore(c)` is correct, (b) and (d) are ruled out.

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