Calculation of Equivalent Mass of an Acid

Given:
- Volume of NaOH solution = 25 ml
- Normality of NaOH solution = N/10
- Volume of acid solution = 20 ml
- Concentration of acid solution = 7.875 gm/L

Solution:

Step 1: Calculation of Number of Moles of NaOH Solution
- Normality of NaOH solution = N/10
- Volume of NaOH solution = 25 ml
- Number of moles of NaOH solution = Normality x Volume (in L)
= (N/10) x (25/1000)
= 0.0025 N

Step 2: Calculation of Number of Moles of Acid Solution
- Concentration of acid solution = 7.875 gm/L
- Volume of acid solution = 20 ml
- Conversion of ml to L = 20/1000 = 0.02 L
- Number of moles of acid solution = Concentration x Volume (in L)
= 7.875 x 0.02/1000
= 0.0001575 moles

Step 3: Calculation of Equivalent Mass of Acid Solution
- Number of moles of NaOH solution = Number of moles of acid solution
- Molecular weight of NaOH = 40 g/mol
- Equivalent weight of NaOH = Molecular weight/Valency
= 40/1
= 40 g/eq
- Equivalent weight of acid = Molecular weight/Valency
= (7.875 g/L) / (0.0001575 moles/L)
= 500 g/eq

Answer: The equivalent mass of the acid solution is 500 g/eq.

Explanation: In this problem, we are given the volume and normality of NaOH solution and the volume and concentration of acid solution. By using the formula of normality and concentration, we can calculate the number of moles of NaOH and acid solutions, respectively. Then, we equate the number of moles of NaOH solution and acid solution because they react in a 1:1 ratio. For the calculation of equivalent mass, we use the formula of equivalent weight, which is the molecular weight of the compound divided by its valency. The equivalent weight of NaOH is 40 g/eq because it has a valency of 1. Finally, we calculate the equivalent weight of the acid using the equivalent weight formula and the given concentration of the acid solution. The equivalent mass of the acid is 500 g/eq.