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

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

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Answer 1 · 2017-08-03T15:51:47

Check out the explanation.

Explanation:

Dissociation or association of protons happens one at a time, not all at once.
Not $H_{3} P O_{4} \Leftrightarrow 3 H^{+} + P O_{4}^{3 -}$ $H_3PO_4 hArr 3H^+ + PO_4^(3-)$
but
$H_{3} P O_{4} \Leftrightarrow H^{+} + H_{2} P O_{4}^{-}$ $H_3PO_4 hArr H^+ + H_2PO_4^-$
$H_{2} P O_{4}^{- \Leftrightarrow} H^{+} + H P O_{4}^{2 -}$ $H_2PO_4^- hArr H^+ + HPO_4^(2-)$
$H P O_{4} \Leftrightarrow H^{+} + P O_{4}^{3 -}$ $HPO_4 hArr H^+ + PO_4^(3-)$

Not $N H_{2}^{-} + 2 H^{+} \Leftrightarrow N H_{4}^{+}$ $NH_2^(-) + 2H^+ hArr NH_4^+$
but
$N H_{2}^{-} + H^{+} \Leftrightarrow N H_{3}$ $NH_2^(-) + H^+ hArr NH_3$
$N H_{3} + H^{+} \Leftrightarrow N H_{4}^{+}$ $NH_3 + H^+ hArr NH_4^+$

Some species are amphoteric, meaning they can act as an acid or base (e.g. water and ammonia).
$N H_{3} + H_{3} O^{+} \Leftrightarrow N H_{4}^{+} + H_{2} O$ $NH_3 + H_3O^+ hArr NH_4^+ + H_2O$

Strong acids and bases dissociate completely. Remember that only the first proton for $H_{2} S O_{4}$ $H_2SO_4$ will completely dissociate. $H S O_{4}^{-}$ $HSO_4^-$ is not a strong acid.

7 strong acids: $H C l, H B r, H I, H C l O_{4}, H C l O_{3}, H N O_{3}, H_{2} S O_{4}$ $HCl, HBr, HI, HClO_4, HClO_3, HNO_3, H_2SO_4$
8 strong bases: $N a O H, K O H, L i O H, R b O H, C s O H, C a {(O H)}_{2},$ $NaOH, KOH, LiOH, RbOH, CsOH, Ca(OH)_2,$
$B a {(O H)}_{2}, S r {(O H)}_{2}$ $Ba(OH)_2, Sr(OH)_2$

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

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

Remember that water goes through self-ionization/self-dissociation.
$H_{2} O + H_{2} O \Leftrightarrow H_{3} O^{+} + O H^{-}$ $H_2O+H_2O hArr H_3O^+ + OH^-$

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.

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

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