Question

On heating a liter of a \[\dfrac {N}{{{\text{ }}2}}\]\[HCl\] solution, \[2.750\] gram of \[HCl\] is lost and the volume of solution becomes\[750{\text{ }}ml\]. The normality of resulting solution will be
A) $0.57$
B) \[0.075\]
C) \[0.057\]
D) \[5.7\]

Answer 1

Hint: In the given question the amount of volume of lost \[HCl\] in the solution has given, according to it we have to find the normality of the resulting solution. As the normality is the measure of concentration equal to the gram equivalent weight per liter of solution.

Complete answer:
The Normality is often denoted by the letter \[N\] and Some of the other units of normality are also expressed as \[eq/{L^{ - 1}}\]. The latter is often used in medical diagnosis. The common equation of normality \[N\] is equal to the gram equivalent weight which is divided by liters of solution.

According to the question for calculating the normality firstly we have to calculate the moles of hydrochloric acid.
So, Moles of \[HCl{\text{ }} = {\text{ }}1 \times \dfrac {1}{2} = 0.5\]
Therefore, the Moles of \[HCl\] lost in solution \[ = {\text{ }}\dfrac {{2.75{\text{ }}}}{{36.5}}{\text{ }} = {\text{ }}0.075\] moles
Thus, the Moles of \[HCl\] left in solution \[ = {\text{ }}0.5{\text{ }}-{\text{ }}0.075{\text{ }} = {\text{ }}0.425\]
Now, the normality of the final solution will be
\[ = {\text{ }}\dfrac {{number{\text{ }}of\;moles{\text{ }}}}{{volume{\text{ }}in{\text{ }}litre}}\]
Putting the values in formula
$ = \dfrac {{0.425\;}}{{\dfrac {{750}}{{1000}}}}{\text{ }}$
So, the normality will be \[ = {\text{ }}0.57{\text{ }}N\]

Hence, the correct answer is option ‘A’.

Note: Normality in terms of chemistry is an expression that is used to measure the concentration of a solution and it is abbreviated as ‘N’ and is sometimes referred to as the equivalent concentration of a solution. Normality is also used in the reactions such as precipitation reactions to measure the number of ions which are probable to precipitate in a specific reaction.