How can we determine the percentage by mass of ammonium ions in an ammonium salt sample?
Calculating Ammonium Ion Content
To determine the percentage by mass of ammonium ions in an ammonium salt sample, we can follow the given procedure involving reactions with potassium hydroxide and hydrochloric acid. Firstly, we need to calculate the amount of hydrochloric acid added, the amount of potassium hydroxide added, and the amount of ammonium ions in the sample.
a) Amount of Hydrochloric Acid Added:
Given:
- Volume of hydrochloric acid = 23.89 mL = 0.02389 L
- Concentration of hydrochloric acid = 0.1032 mol L⁻¹
Using the formula:
Amount of hydrochloric acid added = Concentration × Volume
Amount = 0.1032 mol L⁻¹ × 0.02389 L
Amount = 0.00247 mol or 2.47 mmol
b) Amount of Potassium Hydroxide Added:
Given:
- Volume of potassium hydroxide solution = 50.00 mL = 0.05000 L
- Concentration of potassium hydroxide solution = 0.5493 mol L⁻¹
Using the formula:
Amount of potassium hydroxide added = Concentration × Volume
Amount = 0.5493 mol L⁻¹ × 0.05000 L
Amount = 0.0275 mol or 27.5 mmol
c) Amount of Ammonium Ions:
Since all the hydroxide ions reacted with the ammonium ions in the sample, the amount of ammonium ions is equal to the amount of hydroxide ions.
Amount = 0.0275 mol or 27.5 mmol
d) Percentage by Mass of Ammonium Ions:
To calculate the percentage by mass, we compare the mass of ammonium ions to the total mass of the sample.
Mass of ammonium ions = Amount of ammonium ions × molar mass of ammonium ions
Molar mass of ammonium ions (NH₄⁺) = 18.039 g/mol
Mass of ammonium ions = 0.0275 mol × 18.039 g/mol
Mass = 0.496 g
Percentage by mass of ammonium ions = (Mass of ammonium ions / Mass of the sample) × 100%
Percentage = (0.496 g / 1.988 g) × 100%
Percentage = 24.95%