1.

Which of the following aqueous solutions have highest pH at 25^(@)C ? [Given that at 25^(@)C H_(2)CO_(3) pKa_(1) = 8, pKa_(2) = 12 and H_(3)PO_(4)pKa_(1) = 4, pKa_(2) = 7, pKa_(3) = 13]

Answer»

`10^(-10) M HCl`
`10^(-10) M NaOH`
`10^(-3)M Na_(2)CO_(3)`
`10^(-3) M KH_(2)PO_(4)`

Solution :`10^(-10)MHCl` : ACIDIC solution `pH square 7`
`10^(-10) M NaOH` , Alkaline solution `pH square 7`
`10^(-3)M Na_(2)CO_(3)`, Salt of W.A/S.B `pH= 7+ (1)/(2) [12 + (-3)]= 7+ 4.5= 11.5`
`KH_(2)PO_(4)` is a salt of amphoteric anion. Its pH is GIVEN by the RELATION `(pKa_(1) + pKa_(2))/(2)= 5.5`


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