Question

According to Arrhenius theory, all the given compounds are acids except:

• A. $HCl$
• B. $H_{2}C{O}_3$
• C. $NaCl$
• D. $Mg(OH{)}_2$

Answer 1

Answer: (C), (D)

The correct options are
C $NaCl$
D $Mg(OH{)}_2$

According to Arrhenius theory, an acid is a substance that gives rise to $H^{+}$ ions as the cations, when dissolved in water. Similarly, a base is a substance that gives rise to $O{H}^{-}$ ions as the anions, when dissolved in water.

$NaCl$ and $Mg(OH{)}_2$ dissociates when dissolved in water, as shown below.

$\mathrm{NaCl}\left(\mathrm{aq}\right)\to {\mathrm{Na}}^{+}\left(\mathrm{aq}\right)+{\mathrm{Cl}}^{-}\left(\mathrm{aq}\right)\mathrm{Mg}\left(\mathrm{OH}{)}_2\right(\mathrm{aq})\to {\mathrm{Mg}}^{+}(\mathrm{aq})+{\mathrm{OH}}^{-}(\mathrm{aq})$

In both the cases, $H^{+}$ ions are not released. Hence, according to Arrhenius theory, they are not acids.
Also, $Mg(OH{)}_2$ is a base as it gives $O{H}^{-}$ ions on dissociation and $NaCl$ is a salt.