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

Aug 3, 2017

Check out the explanation.

#### Explanation:

Dissociation or association of protons happens one at a time, not all at once.
Not ${H}_{3} P {O}_{4} \Leftrightarrow 3 {H}^{+} + P {O}_{4}^{3 -}$
but
${H}_{3} P {O}_{4} \Leftrightarrow {H}^{+} + {H}_{2} P {O}_{4}^{-}$
${H}_{2} P {O}_{4}^{-} \Leftrightarrow {H}^{+} + H P {O}_{4}^{2 -}$
$H P {O}_{4} \Leftrightarrow {H}^{+} + P {O}_{4}^{3 -}$

Not $N {H}_{2}^{-} + 2 {H}^{+} \Leftrightarrow N {H}_{4}^{+}$
but
$N {H}_{2}^{-} + {H}^{+} \Leftrightarrow N {H}_{3}$
$N {H}_{3} + {H}^{+} \Leftrightarrow N {H}_{4}^{+}$

Some species are amphoteric, meaning they can act as an acid or base (e.g. water and ammonia).
$N {H}_{3} + {H}_{3} {O}^{+} \Leftrightarrow N {H}_{4}^{+} + {H}_{2} O$

Strong acids and bases dissociate completely. Remember that only the first proton for ${H}_{2} S {O}_{4}$ will completely dissociate. $H S {O}_{4}^{-}$ is not a strong acid.

7 strong acids: $H C l , H B r , H I , H C l {O}_{4} , H C l {O}_{3} , H N {O}_{3} , {H}_{2} S {O}_{4}$
8 strong bases: $N a O H , K O H , L i O H , R b O H , C s O H , C a {\left(O H\right)}_{2} ,$
$B a {\left(O H\right)}_{2} , S r {\left(O H\right)}_{2}$

For strong acids and bases, you use a one-way arrow ($\to$).
For weak acids and bases, you use a two-way arrow ($\Leftrightarrow$).

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

Remember that water goes through self-ionization/self-dissociation.
${H}_{2} O + {H}_{2} O \Leftrightarrow {H}_{3} {O}^{+} + O {H}^{-}$

The reaction is: acid + base $\to$ salt + water.

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