Question

Given,\[250ml\] of a solution contains \[6.3g\]of oxalic acid (mol. wt\[ = 126\]). What is the volume of (in liters) of water to be added to this solution to make it a \[0.1N\]solution?
A.\[750\]
B.\[7.5\]
C.\[0.075\]
D.\[0.75\]

Answer 1

Hint: We need to know that the required volume of water can be found by subtracting the volume of oxalic acid from the total volume. Here first we need to find the normality. And it can be calculated by dividing the number of equivalents of solute by one liter of solution. The oxalic acid is a chemical compound having the molecular formula, \[{H_2}{C_2}{O_4}\]. It is also known as ethanedioic acid which is the simplest carboxylic acid. And the oxalic acid is a white crystalline solid and it will produce colorless solution when it is dissolved in water.

Complete answer:
The volume of water to be added to this solution to make it a \[0.1N\] solution is not equal to\[750\]. Hence, option (A) is incorrect.
The volume of water is not equal to\[7.5\]. Hence, option (B) is incorrect.
The amount of water to make \[0.1N\] solution is not equal to \[0.075\]. Hence, option (C) is incorrect.
To calculate the volume of water, first we need to find out the total volume by using the formula of normality. Let’s see the equation,
\[Normality = \dfrac{{number of equivalents of solute}}{{1literofsolution}}\]
This formula is also written as,
\[Normality = \dfrac{{weight}}{{eq.wt}} \times \dfrac{{1000}}{{V(ml)}} - - - - \left( 1 \right)\]
Given, the weight of oxalic acid is equal to \[6.3g\], molecular weight of oxalic acid is equal to\[126g/L\]. Hence, the equivalent of oxalic acid is equal to \[63g\] and the normality of oxalic acid is equal to \[0.1N\]. Substitute the given values in equation one.
\[0.1 = \dfrac{{6.3}}{{63}} \times \dfrac{{1000}}{{V(ml)}}\]
By rearranging this equation, will get
\[V = \dfrac{{6.3}}{{63}} \times \dfrac{{1000}}{{0.1}}\]
By simplifying the equation, will get the value of V, (total volume)
\[V = 1000ml = 1slitre\]
Volume of water\[ = \]total volume – volume of oxalic acid
\[250ml\]of oxalic acid is converted into L. so, \[250ml = 0.25L\]
Therefore,
Volume of water $ = 1 - 0.25 = 0.75L$

Hence, option (D) is correct.

Note:
The volume of water to be added to this solution to make it a \[0.1N\] solution can be found out by using the equation of normality. The normality is known as equivalent concentration. It is expressed as the number of mole equivalents present in the one liter of the solution. And the molarity is the number of moles of solute present in one liter of solution.