Question #25ba6

1 Answer
Dwight
Oct 14, 2017

The alkalinity is due to the phosphate ion, #PO_4^(3-)# . Details follow.

Explanation:

The phosphate ion has a limited ability to gain #H^+# (they bond to the lone pairs of the O atoms in the #PO_4^(3-)# ion).

When this happens in aqueous solution, the #H^+# are taken from molecules of water as follows:

#H_2O+PO_4^(3-) rarr HPO_4^(2-) + OH^-#

That is, the water molecule is pulled apart, such that one piece is #H^+# and the other is #OH^-#.

This changing of #H_2O# into #OH^-# is called hydrolysis and is responsible for the solution becoming basic.

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