Question

How many electrons are transferred in the following reaction?

(The reaction is unbalanced.)

Mg(s) + Al3+(aq) → Al(s) + Mg2+(aq)

Answer 1

3Mg +2Al^3 ⇆ 3 Mg^2+ + 2Al

In this reaction 6 electrons are transferred

Step-by-step explanation:

Step 1: The half reactions

Mg -2e- ⇆ Mg^2+

Al^3+ +3e- ⇆ Al

Step 2: Balance both equations

3*(Mg -2e- ⇆ Mg^2+)

2(Al^3+ +3e- ⇆ Al)

3Mg -6e- ⇆ 3Mg^2+

2Al^3+ +6e- ⇆ 2Al

Step 3: The netto reaction

3Mg +2Al^3 ⇆ 3 Mg^2+ + 2Al

In this reaction 6 electrons are transferred

Answer 2

6

Step-by-step explanation:

Oxidation reaction is defined as the chemical reaction in which an atom looses its electrons. The oxidation number of the atom gets increased during this reaction.

`X\rightarrow X^(n+)+ne^-`

Reduction reaction is defined as the chemical reaction in which an atom gains electrons. The oxidation number of the atom gets reduced during this reaction.

`X^(n+)+ne^-\rightarrow X`

For the given chemical reaction:

`Mg(s)+Al^(3+)(aq.)\rightarrow Al(s)+Mg^(2+)(s)`

The half cell reactions for the above reaction follows:

Oxidation half reaction:
`Mg\rightarrow Mg^(2+)+2e^-`

Reduction half reaction:
`Al^(3+)+3e^-\rightarrow Al`

Magnesium is loosing 2 electrons to form the magnesium cation. Thus, it is getting oxidized. Aluminum anion is gaining 3 electrons to form Aluminum. Thus, it is getting reduced.

Thus, balancing the half-reactions as:-

Oxidation half reaction:
`3Mg\rightarrow 3Mg^(2+)+6e^-`

Reduction half reaction:
`2Al^(3+)+6e^-\rightarrow 2Al`

Thus, total number of electrons transferred = 6