1.

If K_(2) and K_(2)are theionizationconsatnats of H_(3)NCHRCOOH and H_(3)overset(+)(N)CHRCOO^(-) , respectively , the pH of the solutionat theisoelectric point is .

Answer»

`pH = pK_(1) + pK_(2)`
`pH = (pK_(1) pK_(2))^(1//2)`
`pH = (pK_(1) + pK_(2))^(1//2)`
`pH = (pK_(1) + pK_(2))//2`

Solution :`H_(3) overset(+)(N) UNDERSET("LOW pH")overset(R)overset(|)(CH)COOH underset(H^(+))overset(OH^(-))(hArr) underset("Intermediate pH")(H_(3)overset(+)(N)overset(R)overset(|)(CH)COO^(-)) underset(H^(+))overset(OH^(-))hArr H_(2)N underset("HighpH")(H_(2)N overset(R)overset(|)CH)COO^(-)`
`k_(1) =([H_(3)overset(+)NCHRCOO^(-)][H^(+)])/([H_(3) overset(+)NCHROOH]) , K_(2) = ([H_(2)NCHRCOO^(-)][H^(+)])/([H_(3) overset(+)NCHRCOO^(-)])`
Thus , `K_(1)K_(2) = ([H_(2)NCHRCOO^(-)][H^(+)]^(2))/([H_(3)overset(+)NCHROOH])`
At theisoelection point `[H_(2)NCR RCOO^(-)] = [H_(3)N^(+) CHRCOOH]`
`k_(1)k_(2) = [H^(+)]^(2)`
`2 log [H^(+)] =log K_(1) + log K_(2)`
`RARR ""-2log[H^(+)] = - logK_(1)- log K_(2)`
`2pH = pK_(1) + pH_(2) rArr pH= (pHk_(1) + pK_(2))//2`


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