# Classify each as a strong or weak acid or base:

Classify each as a strong or weak acid or base: (a) $HOC{H}_{2}C{H}_{2}N{H}_{2}$, (b) ${H}_{2}Se{O}_{4}$, (c) $H{S}^{-}$, (d) $B{\left(OH\right)}_{3}$
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macalpinee3

Step 1
a) $HOC{H}_{2}C{H}_{2}N{H}_{2}$
First let us write its dissociation reaction in water.
$HOC{H}_{2}C{H}_{2}N{H}_{2}+{H}_{2}O⇌O{H}^{-1}+HOC{H}_{2}C{H}_{2}N{H}_{3}^{+}$
$HOC{H}_{2}C{H}_{2}N{H}_{2}$ is basic because it produced $O{H}^{-}$ion. Since it is an amine,
$HOC{H}_{2}C{H}_{2}N{H}_{2}$ is a weak base.
Step 2
b) ${H}_{2}Se{O}_{4}$
First let us write its dissociation in water.
${H}_{2}SeO4$ is acidic because it produced ${H}^{+}$ion. Since it is not a hydrohalic acid but an oxoacid, let us solve for the number of O and H atoms in the atoms. Their difference should be greater than or equal to 2.
There are 4O and 2H. $4-2=2$ which is equal to 2. Therefore,
${H}_{2}Se{O}_{4}$ is a strong acid.
Step 3
c) First let us write its dissociation reaction in water.
$H{S}^{-}⇌{H}^{+}+{S}^{2-}$
$HS{O}^{-}$ is acidic because it produced ${H}^{+}$ ion. Since it is not a hydrohalic acid nor an oxoacid, $H{S}^{-}$ is a weak acid.
Step 4
d) $B{\left(OH\right)}_{3}$
First let us write its reaction in water.
$B{\left(OH\right)}_{3}+{H}_{2}O⇌B{\left(OH\right)}_{4}^{-}+{H}^{+}$
$B{\left(OH\right)}_{3}$ is acidic because it produced ${H}^{+}$ ion. Since it is not a hydrohalic acid but an oxoacid, let us solve for the number of O and H atoms in the atoms. Their difference should be greater than or equal to 2.
There are 4O and 4H. $4-4=0$ which is less to 2. Therefore, $B{\left(OH\right)}_{3}$ is a weak acid.

Jillian Edgerton
a) $B{\left(OH\right)}_{3}$ is boric acid, not a hydroxide in the sense of the ionic hydroxides of Group 1,2, or the transition metals. It's more commonly written as ${H}_{3}B{O}_{3}$, and it is protonated borate, similar to sulfate, phosphate, or carbonate
b) Not because it's not listed as one of the strong acids, but the electronegativity of the selenium is not high enough to pull enough electron density off of the oxygens to make the hydrogens extremely acidic.
c) Through it can act as either (acting as a base to go to hydrogen sulfide or as an acid to go to sulfide ion), bisulfide tends to be more acidic than basic.
d) Ethanolamine acts as a base as the amino group can be protonated. There is almost no tendency for the alcohol group to get deprotonated.