What are some common mistakes students make with acid and base dissociation?

1 Answer
Aug 3, 2017

Answer:

Check out the explanation.

Explanation:

Dissociation or association of protons happens one at a time, not all at once.
Not #H_3PO_4 hArr 3H^+ + PO_4^(3-)#
but
#H_3PO_4 hArr H^+ + H_2PO_4^-#
#H_2PO_4^- hArr H^+ + HPO_4^(2-)#
#HPO_4 hArr H^+ + PO_4^(3-)#

Not #NH_2^(-) + 2H^+ hArr NH_4^+#
but
#NH_2^(-) + H^+ hArr NH_3#
#NH_3 + H^+ hArr NH_4^+#

Some species are amphoteric, meaning they can act as an acid or base (e.g. water and ammonia).
#NH_3 + H_3O^+ hArr NH_4^+ + H_2O#

Strong acids and bases dissociate completely. Remember that only the first proton for #H_2SO_4# will completely dissociate. #HSO_4^-# is not a strong acid.

7 strong acids: #HCl, HBr, HI, HClO_4, HClO_3, HNO_3, H_2SO_4#
8 strong bases: #NaOH, KOH, LiOH, RbOH, CsOH, Ca(OH)_2,#
#Ba(OH)_2, Sr(OH)_2#

For strong acids and bases, you use a one-way arrow (#->#).
For weak acids and bases, you use a two-way arrow (#hArr#).

HF is not a strong acid. Because fluorine is highly electronegative, it will keep hydrogen.

Remember that water goes through self-ionization/self-dissociation.
#H_2O+H_2O hArr H_3O^+ + OH^-#

The reaction is: acid + base #-># salt + water.

Not all metals react with acid (e.g. copper, gold, silver, platinum). This is based on the activity series.