Question

Which of the following reactions are redox reactions?

Check all that apply. Check all that apply

. Al(s)+3Ag+(aq) = Al3+(aq)+3Ag(s)

SO3(g)+H2O(l) = H2SO4(aq)

Ba(s)+Cl2(g) = BaCl2(s)

Mg(s)+Br2(l) = MgBr2(s)

Answer 1

Concepts and reason

The concept used to solve this problem is based on redox reactions.

A redox reaction is a type of reaction which involves transfer of electrons among two species. This reaction is also called oxidation-reduction reaction.

Fundamentals

In oxidation process, there is an increase in oxidation state of an atom, ion or molecule by losing the electrons.

In reduction process, there is a decrease in oxidation state of an atom, ion or molecule by accepting the electrons.

Write the balanced chemical equation between ${\rm{S}}{{\rm{O}}_3}$ and water as follow.

${\rm{S}}{{\rm{O}}_3}\left( g \right){\rm{ + }}{{\rm{H}}_2}{\rm{O}}\left( l \right) \to {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\left( s \right)$

Now write the oxidation number of each element in the reaction.

$\begin{array}{l}\\{\rm{S}}{{\rm{O}}_3}\left( g \right) + {{\rm{H}}_2}{\rm{O}}\left( l \right) \to {{\rm{H}}_2}{\rm{S}}{{\rm{O}}_4}\left( s \right)\\\\ + 6{\rm{ }} - {\rm{2 }} + 1 - 2{\rm{ }} + 1 + 6 - 2\\\end{array}$

From this reaction, it is clear that there is no change in oxidation number of atoms.

Due to this, this reaction is not a redox reaction.

Write the balanced chemical equation between aluminum and aqueous solution of silver as follow.

${\rm{Al}}\left( s \right){\rm{ + 3A}}{{\rm{g}}^ + }\left( {aq} \right) \to {\rm{A}}{{\rm{l}}^{3 + }}\left( {aq} \right){\rm{ + 3Ag}}\left( s \right)$

Now write the oxidation number of each element in the reaction.

$\begin{array}{l}\\{\rm{Al}}\left( s \right){\rm{ + 3A}}{{\rm{g}}^ + }\left( {aq} \right) \to {\rm{A}}{{\rm{l}}^{3 + }}\left( {aq} \right){\rm{ + 3Ag}}\left( s \right)\\\\{\rm{ 0 }} + {\rm{1 }} + {\rm{3 0}}\\\end{array}$

From this reaction, it is clear that Aluminum undergoes oxidation and silver undergoes reduction.

Due to this, this reaction is redox reaction.

Write balanced chemical equation as follow.

${\rm{Ba}}\left( s \right){\rm{ + C}}{{\rm{l}}_2}\left( g \right) \to {\rm{BaC}}{{\rm{l}}_2}\left( s \right)$

Now write the oxidation number of each element in the reaction.

$\begin{array}{l}\\{\rm{Ba}}\left( s \right){\rm{ + C}}{{\rm{l}}_2}\left( g \right) \to {\rm{BaC}}{{\rm{l}}_2}\left( s \right)\\\\{\rm{0 0 }} + 2 - 1\\\end{array}$

In this reaction, Ba undergoes oxidation and Cl undergoes reduction.

This reaction is redox reaction.

Write balanced chemical equation as follow.

${\rm{Mg}}\left( s \right){\rm{ + B}}{{\rm{r}}_2}\left( g \right) \to {\rm{MgB}}{{\rm{r}}_2}\left( s \right)$

Now write the oxidation number of each element in the reaction.

$\begin{array}{l}\\{\rm{Mg}}\left( s \right){\rm{ + B}}{{\rm{r}}_2}\left( g \right) \to {\rm{MgB}}{{\rm{r}}_2}\left( s \right)\\\\{\rm{0 0 }} + 2 - 1\\\end{array}$

In this reaction, Mg undergoes oxidation and Br undergoes reduction.

This reaction is redox reaction.

Ans:

The reactions 1, 3 and 4 are redox reactions.