Question

Di-phosphorus pentoxide reacts with water to produce phosphoric acid (${{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{\text{4}}}$). How do you write the balanced equation for this reaction?

Answer 1

Hint: Di-phosphorus pentoxide always exists in the dimer form in the nature because of the reactive behavior of phosphorus atom and for balancing any chemical equation, we have to maintain equal molecularity of each atom present on both sides of chemical reaction.

Complete answer:
Given that, Di-phosphorus pentoxide reacts with water to produce phosphoric acid and chemical reaction for this is shown as follow:
 ${{\text{P}}_{\text{4}}}{{\text{O}}_{{\text{10}}\left( {\text{s}} \right)}}{\text{ + }}{{\text{H}}_{\text{2}}}{{\text{O}}_{\left( {\text{l}} \right)}} \to {{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{{\text{4}}\left( {{\text{aq}}} \right)}}$
For balancing the above given equation we have to consider following points in mind:
-First we calculate the number of each atom on the left hand side as well as on the right hand side of the given chemical equation.
-So on the left hand side or reactant side four phosphorus atom (${\text{P}}$) and on the right hand side or product side of the chemical reaction only one phosphorus (${\text{P}}$) atom is present.
-On the left hand side ten atoms of oxygen (${\text{O}}$) are present but on the right hand side only four oxygen atoms are present which is not correct.
- Similarly, on the left side two hydrogen atoms (${\text{H}}$) and on the right side three hydrogen atoms (${\text{H}}$) are present which is not correct.
So, we will balance the above given reaction by the following manner so that each atom will have the same molecularity on the reactant side as well as on the product of the reaction. And balanced equation is shown as:
${{\text{P}}_{\text{4}}}{{\text{O}}_{{\text{10}}\left( {\text{s}} \right)}}{\text{ + 6}}{{\text{H}}_{\text{2}}}{{\text{O}}_{\left( {\text{l}} \right)}} \to 4{{\text{H}}_{\text{3}}}{\text{P}}{{\text{O}}_{{\text{4}}\left( {{\text{aq}}} \right)}}$
-In the above balanced equation four phosphorus atoms (${\text{P}}$), twelve hydrogen atoms (${\text{H}}$) and sixteen oxygen (${\text{O}}$) atoms are present on the left hand side as well as on the right hand side of the chemical reaction also.

Note:
Here some of you may think order of reaction and molecularity of reaction are the same things but that will be true only for the elementary (single step reaction) reactions only.