Three reactions involving H_(2)PO_(4)^(-) are given below : (i) H_(3)PO_(4) + H_(2)O rarrH+_(3)O^(+) + H_(2)PO_(4)^(-) (ii) H_(2)PO_(4)^(-) + H_(2)O rarr HPO_(4)^(2-) + H_(3)O^(+) (iii) H_(2)PO_(4)^(-) + OH^( -) rarr H_(3)PO_(4) + O^(2-) In which of theabove does H_(2)PO_(4)^(-) act as an acid ?

Three reactions involving H_(2)PO_(4)^(-) are given below : (i) H_(3)

1.	Three reactions involving H_(2)PO_(4)^(-) are given below : (i) H_(3)PO_(4) + H_(2)O rarrH+_(3)O^(+) + H_(2)PO_(4)^(-) (ii) H_(2)PO_(4)^(-) + H_(2)O rarr HPO_(4)^(2-) + H_(3)O^(+) (iii) H_(2)PO_(4)^(-) + OH^( -) rarr H_(3)PO_(4) + O^(2-) In which of theabove does H_(2)PO_(4)^(-) act as an acid ?
Answer» (iii)only (i) only (ii) ony (i) and (ii) SOLUTION :In (i), in the reverse REACTION, `H_(2)PO_(4)^(-)` is accepting a proton. Hence,it is a base (ii), `H_(2)PO_(4)^(-)` is donating a proton which is ACCEPTED by `H_(2)O`. Hence it is an acid. In (iii) , `H_(2)PO_(4)^(-)` is accepting a proton. Hence it is a base Thus, only in (ii), `H_(2)PO_(4)^(-)` acts an acid.