# How are the following reaction described?

## $\left(a\right) . H X \left(a q\right) + M O H \left(a q\right) \rightarrow M X + {H}_{2} O$ $\left(b\right) . M \left(s\right) + {H}_{2} O \rightarrow M O H + \frac{1}{2} {H}_{2}$ $\left(c\right) . F e + 2 F {e}^{3 +} \rightarrow 3 F {e}^{2 +}$ What does $\left(a q\right)$ as a descriptor of a reactant or product?

Feb 9, 2017

$\text{(a) an acid-base reaction}$

#### Explanation:

$\text{(b) a redox reaction}$

$\text{(c) a comproportionation reaction}$.

$\left(a q\right)$ simply means the $\text{aquated ion}$, or the ionic species in aqueous solution. For $C u \left(S {O}_{4}\right) \left(a q\right)$ this means $C {u}^{2 +}$ and $S {O}_{4}^{2 -}$, where in aqueous solution $C {u}^{2 +}$ exists as the coordination complex ${\left[C u {\left(O {H}_{2}\right)}_{6}\right]}^{2 +}$, which has a truly beautiful blue colour.

In $\text{(c)}$, this is a subset of redox reaction, but here, instead of one species being reduced, and another species oxidized, which conventionally occurs, as for $\text{(b)}$, here the reactants are in different oxidations states, i.e. ${N}^{- I I I}$ in $\text{ammonia}$, and ${N}^{+ I}$ in $\text{dinitrogen monoxide}$ (note that we could formally assign oxidation states of ${N}^{0}$, and ${N}^{+ I I}$ but the average oxidation is ${N}^{+ I}$), these formally exchange electrons so that their product gives ${N}^{+ I}$, a formal comproportionation.

I assume you are a first/second year undergrad. If you are an A-level student you don't need to know about $\text{comproportionation}$.