some ammonia gas is dissolved in water. The exact concentration of the solution is unknown and has to be determined. Describe an experiment that would determine the concentration of the aqueous ammonia.
How about titrating it with an acid such as HCl? You work out the details.
To determine the concentration of the aqueous ammonia solution, you can perform a titration experiment with a known concentration of an acid solution. Here's a step-by-step procedure for this experiment:
1. Gather the necessary equipment: You will need a burette, a flask, a pH meter or indicator, a standardized acid solution (e.g., sulfuric acid or hydrochloric acid), a pipette, and a stirrer.
2. Measure a fixed volume of the unknown ammonia solution: Use a pipette to accurately measure a fixed volume (e.g., 25 mL) of the aqueous ammonia solution into a flask.
3. Set up the titration apparatus: Attach the burette to a stand and fill it with the standardized acid solution. Make sure to record the initial volume of the acid solution in the burette.
4. Titrate the ammonia solution: Slowly add the acid solution from the burette into the flask containing the ammonia solution while stirring continuously. The acid will react with the ammonia in a neutralization reaction.
5. Observe the endpoint: As the acid is added, monitor the pH of the solution using a pH meter or indicator. The endpoint is reached when the pH decreases significantly or when a specific color change is observed. This indicates that all the ammonia has reacted with the acid.
6. Record the final volume of the acid solution: Stop adding the acid solution once the endpoint is achieved. Record the final volume of the acid solution in the burette.
7. Calculate the concentration of the ammonia solution: Subtract the initial volume of the acid solution from the final volume to determine the volume of acid used for titration. Use the stoichiometry of the reaction between ammonia and the acid to calculate the concentration of the ammonia solution.
The equation for the reaction between ammonia (NH3) and an acid (H+):
NH3 + H+ → NH4+
By knowing the volume of acid required for neutralization and the concentration of the acid solution, you can determine the concentration of the ammonia solution.