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${{P}_{2}}{{O}_{5}}+{{H}_{2}}O\to {{H}_{3}}P{{O}_{4}}$

The normality of the phosphoric acid formed is (The volume of solution is 1L)

(a) 2

(b) 12

(c) 24

(d) 4

Answer
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Molarity: The molarity of the solution is defined as the number of moles of the solute present per liter. It is represented by the symbol, M.

\[Molarity=\dfrac{\text{Moles of the solute}}{\text{Volume of the solution}}\]

Moles of the solute can be calculated by:

\[Moles=\dfrac{\text{mass of the solute}}{\text{molar mass of the solute}}\]

The normality of the solution is defined as the number of grams equivalent of the solute present in liters. It is represented by the symbol, N.

\[Normality=\dfrac{\text{Gram equivalent of the solute}}{\text{Volume of the solution}}\]

First, let us balance the given equation:

${{P}_{2}}{{O}_{5}}+{{H}_{2}}O\to {{H}_{3}}P{{O}_{4}}$

After balancing the equation will be:

$2{{P}_{2}}{{O}_{5}}+6{{H}_{2}}O\to 4{{H}_{3}}P{{O}_{4}}$

And the volume of the solution is 1 L. (Given)

So, from the balanced equation we can that there are 4 moles of phosphoric acid in 1 L of solution.

From this we can calculate the molarity of the solution:

\[Molarity=\dfrac{\text{Moles of the solute}}{\text{Volume of the solution}}\]

So, by putting the values in the above equation:

\[Molarity=\dfrac{\text{Moles of the solute}}{\text{Volume of the solution}}=\dfrac{4}{1}=4\]

The molarity is 4.

With molarity, we can find the normality of the solution.

Normality of the acid = molarity x basicity.

Phosphoric acid has basicity 3 because of the presence of hydrogen ions.

So, normality of the phosphoric acid will be:

$normality=\text{ 4 x 3 = 12 N}$

Hence, the normality is 12 N.