4.86P - Chemistry: Molecular Nature Of Matter And Change

Question

Give one example of a combination reaction that is a redox reaction and another that is not a redox reaction.

Step-by-Step Solution

Answer

You need to provide one example of a combination reaction that is a redox reaction and another that is not a redox reaction.

Step 1: Solution of the Problem

Reaction of metal and non-metal forms an ionic compound is an example of redox combination reaction.

 

Reaction of metal oxide with water forms an acid is an example of normal combination reaction.

Step 2: Redox combination reaction

The reaction of metal and non-metal forms of an ionic compound is an example of a redox combination reaction.

Example:

 

$2Mg\left(g\right)+O_2\left(g\right)\to 2MgO\left(g\right)$

 

Step 3: Explanation of the solution

Oxidation no of element Magnesium and oxygen is 0.

 

Oxidation no of oxygen in MgO is -2 and magnesium is +2.

 

The oxidation no of oxygen is 0 in O₂ decreases to -2 in MgO. Therefore, O₂ undergoes reduction.

The oxidation no of magnesium is 0 in Mg increases to +2 in MgO. Therefore, Mg undergoes oxidation.

Step 4: Normal combination reaction

Reaction of metal oxide with water forms an acid is an example of normal combination reaction.

Example:

 $CaO\left(s\right)+H_{2}O\left(l\right)\to Ca{\left(OH\right)}_2\left(aq\right)$$CaO\left(s\right)+H_{2}O\left(l\right)\to Ca{\left(OH\right)}_2\left(aq\right)$

Step 5: Explanation of the solution

Oxidation no of oxygen in CaO is -2.

 

Oxidation no of calcium in CaO is +2.

 

Oxidation no of oxygen in Ca(OH)₂ is also -2.

 

Oxidation no of calcium in Ca(OH)₂ is also +2.

 

The oxidation no of oxygen and calcium doesn’t change in the whole reaction. Hence, it is not a redox reaction; it is a normal combination reaction.