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Answer:
The initial concentration of ammonia is 0.14 M and the pH of the solution at equivalence point is 5.20
<u>Explanation:</u>
To calculate the number of moles for given molarity, we use the equation:
.....(1)
Molarity of HCl solution = 0.164 M
Volume of solution = 23.8 mL = 0.0238 L (Conversion factor: 1 L = 1000 mL)
Putting values in equation 1, we get:
The chemical equation for the reaction of ammonia and HCl follows:
By Stoichiometry of the reaction:
1 mole of HCl reacts with 1 mole of ammonia
So, 0.0035 moles of HCl will react with = of ammonia
- Calculating the initial concentration of ammonia by using equation 1:
Moles of ammonia = 0.0035 moles
Volume of solution = 25 mL = 0.025 L
Putting values in equation 1, we get:
By Stoichiometry of the reaction:
1 mole of ammonia produces 1 mole of ammonium ion
So, 0.0035 moles of ammonia will react with = of ammonium ion
- Calculating the concentration of ammonium ion by using equation 1:
Moles of ammonium ion = 0.0035 moles
Volume of solution = [23.8 + 25] mL = 48.8 mL = 0.0488 L
Putting values in equation 1, we get:
- To calculate the acid dissociation constant for the given base dissociation constant, we use the equation:
where,
= Ionic product of water =
= Acid dissociation constant
= Base dissociation constant =
The chemical equation for the dissociation of ammonium ion follows:
The expression of for above equation follows:
We know that:
Putting values in above expression, we get:
To calculate the pH concentration, we use the equation:
We are given:
Hence, the initial concentration of ammonia is 0.14 M and the pH of the solution at equivalence point is 5.20