Question

Balance each of the following redox reactions and classify it as a combination, decomposition, or displacement reaction:

$\left(\mathit{a}\right)\mathit{M}\mathit{g}\left(\mathit{s}\right)\mathbf{+}{\mathit{H}}_{\mathbf{2}}\mathit{O}\left(\mathit{g}\right)\mathbf{\to }\mathit{M}\mathit{g}{\left(\mathit{O}\mathit{H}\right)}_{\mathbf{2}}\left(\mathit{s}\right)\mathbf{+}{\mathit{H}}_{\mathbf{2}}\left(\mathit{g}\right)$

$\left(\mathit{b}\right)\mathit{C}\mathit{r}{\left(\mathit{N}{\mathit{O}}_3\right)}_{\mathbf{3}}\left(\mathit{a}\mathit{q}\right)\mathbf{+}\mathit{A}\mathit{l}\left(\mathit{s}\right)\mathbf{\to }\mathit{A}\mathit{l}{\left(\mathit{N}{\mathit{O}}_3\right)}_{\mathbf{3}}\left(\mathit{a}\mathit{q}\right)\mathbf{+}\mathit{C}\mathit{r}\left(\mathit{s}\right)$

$\left(\mathit{c}\right)\mathit{P}{\mathit{F}}_{\mathbf{3}}\left(\mathit{g}\right)\mathbf{+}{\mathit{F}}_{\mathbf{2}}\left(\mathit{g}\right)\mathbf{\to }\mathit{P}{\mathit{F}}_{\mathbf{5}}\left(\mathit{g}\right)$

Short answer

The classification of the given reactions are:

(a) Displacement reaction

(b) Displacement reaction

(c) Combination reaction

Step-by-step solution

Write balanced reaction of equation (a)

The given reaction is:

$Mg\left(s\right)+H_{2}O\left(g\right)\to Mg{\left(OH\right)}_2\left(s\right)+H_2\left(g\right)$

The balanced reaction is:

$Mg\left(s\right)+2H_{2}O\left(g\right)\to Mg{\left(OH\right)}_2\left(s\right)+H_2\left(g\right)$

The given redox reaction is a displacement reaction.

The Mg atom replaces two Hatoms from and forms $Mg{\left(OH\right)}_2.$

Write balanced reaction of equation (b)

The given reaction is:

$Cr{\left(N{O}_3\right)}_3\left(aq\right)+Al\left(s\right)\to Al{\left(N{O}_3\right)}_3\left(aq\right)+Cr\left(s\right)$

The balanced reaction is:

$Cr{\left(N{O}_3\right)}_3\left(aq\right)+Al\left(s\right)\to Al{\left(N{O}_3\right)}_3\left(aq\right)+Cr\left(s\right)$

The given redox reaction is a displacement reaction.

The aluminum atom replaces chromium atom from $Cr{\left(N{O}_3\right)}_3$ and forms $Al{\left(N{O}_3\right)}_3.$

Determine the type of reaction of equation (c)

The given reaction is:

$P{F}_3\left(g\right)+F_2\left(g\right)\to P{F}_5\left(g\right)$

The balanced reaction is:

$P{F}_3\left(g\right)+F_2\left(g\right)\to P{F}_5\left(g\right)$

The given redox reaction is a combination reaction.