Question

Normality of 0.025 M \[Ba{\left( {OH} \right)_2}\]is:
A. 0.05
B. 0.25
C. 0.5
D. 0.025

Answer 1

Hint:Barium hydroxide i.e. \[Ba{\left( {OH} \right)_2}\] is a chemical compound which is considered to be a strong base owing to its ability to separate completely into barium ions as well as hydroxide ions when it is dissolved in water.

Complete answer:
Normality or equivalent concentration of solution refers to a measure of concentration which is the gram equivalent weight per unit volume of solution (in litre). Normality of a solution can be calculated with the following formula:
$
  Normality = \dfrac{{Number{\text{ }}of{\text{ }}gram{\text{ }}equivalents}}{{Volume{\text{ }}of{\text{ }}solution{\text{ }}in{\text{ }}litres}} \\
  or \\
  Normality = \dfrac{{Weight}}{{Equivalent{\text{ weight}}}} \times \dfrac{{1000}}{{V(mL)}}
 $
This formula can be elaborated further to write it in terms of molarity.
$
  Normality = \dfrac{{Weight}}{{\dfrac{{Molecular{\text{ }}weight}}{n}}} \times \dfrac{{1000}}{{V(mL)}} = n \times \dfrac{{Weight}}{{Molecular{\text{ }}weight}} \times \dfrac{{1000}}{{V(mL)}} \\
  Normality = n \times Molarity
 $
(Here, n corresponds to the $e^-$ transfer)
In the question we are given the Molarity of \[Ba{\left( {OH} \right)_2}\] as 0.025 M. We have to find out the Normality.
We know that \[Ba{\left( {OH} \right)_2}\] is a strong base and it will dissociate completely on dissolution. Thus we can write the equation as follows:
\[Ba{\left( {OH} \right)_2} \to B{a^{2 + }} + 2O{H^ - }\]
The equation indicates that each \[Ba{\left( {OH} \right)_2}\]​ molecule dissociates to form 2 \[O{H^ - }\].
Thus, n = 2
Molarity = 0.025 M
Now substituting the values in normality formula, we get:
$Normality = 2 \times 0.025 = 0.050$ N

Hence, the correct answer is Option A.

Note:
1. Never get confused between the use of normality, molarity and molality as a measure of concentration. Molarity is the number of moles of solute particles per litre of solution. Normality is the gram equivalent weight per litre of the solution. Molality is the number of moles of solute particles per kilogram of solvent.
2. Most of the time, molarity is being preferred as the most suitable measure of concentration. In cases when the temperature of an experiment changes, then molality is preferred over other units of concentration. Normality is preferred most often in case of titration calculations.