Question

Normality of 1 molar sodium carbonate is:
A.2 N
B.1 N
C.\[0.5{\kern 1pt} {\text{ N}}\]
D.\[1.5{\kern 1pt} {\text{ N}}\]

Answer 1

Hint: The normality can be calculated using the relation between the moles and number of equivalents. Multiply the n factor value with the molarity and we will get the value of normality.

Complete step by step solution:
Normality is defined as the number of gram equivalents of the solute divided by the volume of solution.
\[{\text{Normality}} = \dfrac{{{\text{No}}{\text{. of equivalents}}}}{{{\text{Volume}}}}\]
 Number of gram equivalents is defined as the ratio of the mass of solute to the equivalent weight. Equivalent weight is molecular mass divided by 2. Hence using the above definition we can rewrite the formula as:
\[{\text{Normality}} = \dfrac{{{\text{mass}} \times {\text{n}} - {\text{factor}}}}{{{\text{molar mass }} \times {\text{Volume}}}}\]
Molarity is defined as the ratio of number of moles to the volume of solution and number of moles is the ratio of mass and molar mass. Hence the formula will become:
\[{\text{Normality}} = {\text{ Molarity}} \times {\text{n}} - {\text{factor}}\]
The n factor or also called valency for a salt is defined as the number of electrons gained or lost by 1 mole of the salt.
The molecular formula for sodium carbonate is \[{\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3}\] . The dissociation of sodium carbonate occurs as:
\[{\text{N}}{{\text{a}}_2}{\text{C}}{{\text{O}}_3} \to 2{\text{N}}{{\text{a}}^ + } + {\text{CO}}_3^{2 - }\]
As we can see that one mole of sodium carbonate brings a change of 2 electrons in the reaction. Hence the n – factor is 2. The molarity of the solution is given to us as 1 molar.
Hence we will calculate the normality as:
\[{\text{Normality}} = {\text{ }}1 \times 2 = 2\]

Hence, the correct option is (A).

Note:
n – factor is calculated differently for various types of species: For an acid n factor is calculated as the number of hydrogen ions given by the acid during it dissociates, For a base n factor is the number of hydroxide ions given during dissociation.