Question

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

Answer 1

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.