DRAFT: This module has unpublished changes.

Introduction:

The goal for this experiment is to determine the stoichiometric ratio between silver and an unknown ion. By mixing various solutions of these two ions together, and varying the ratios of one to the other (but keeping the volume constant), we can remove the ions in varying proportions via the precipitate formed. This can be used to calculate the stoichiometric ratios of ions in solution.

 

Given that the conductivity of a solution is dependent upon the amount of ions within it, I hypothesize that by combing these two solutions, having them react, and measuring the conductivity of each solution, that we should then be able to recognize the least conductive of the solutions as having a stoichiometric ratio that is closest to the theoretical stoichiometric ratio for silver ions and the unknown ions. By examining the distribution of the data gathered, we should be able to find that the most feasible of these ratios falls somewhere between the most conductive, and second most conductive solution.

 

Equipment:

  • 9 Test Tubes
  • Test Tube Rack
  • (2) Graduated Pipet, 10-mL
  • Rubber Bulb
  • Parafilm®
  • Beaker, glass, 100-mL
  • 0.01 M Silver Nitrate, 50-mL
  • Unknown Solution, 50-mL
  • Data Collection System
  • Conductivity Sensor
  • Wash Bottle with Deionized Water

 

Methods:

  • Gathered 9 Test Tubes, rack, and pipets and bulbs (Henceforth, assume them to be together, unless mentioned otherwise). Labeled test tubes with orange tape, as 1-9.
  • Measured the prescribed amount of silver nitrate with one of the pipets, and deposited it into the associated test tube. Cleaned the pipettes, and placed them in the designated area for them to dry.
  • Measured the prescribed amount of the unknown solution with the other pipet, and deposited it into the associated test tube, before covering each with Parafilm®, and shaking each thoroughly, to ensure that the solutions are completely mixed.
  • Measured the conductivity of each solution (which had now had formed a precipitate), taking care to rinse the conductivity sensor with deionized water (including within the holes on the sides of the sensor), following each use.
  •  Collected the wash in the 100-mL beaker. Disposed of the contents of the beaker and test tubes in the appropriate container, cleaned them, and set them aside to dry. Returned all equipment to its point of origin.

 

Data Analysis:

Of these solutions, 6 provided the lowest overall conductivity, however, by analysis, we can recognize that the actual low point falls somewhere between 6 and 7 (and as such, so does the closest feasible stoichiometric ratio). From this, we can conclude that the experimental stoichiometric ratio for the silver ions and unknown ions is most likely to be 2:1, with a balanced equation of:

 

Conclusion:

The goal for this experiment is to determine the stoichiometric ratio between silver and an unknown ion. By mixing various solutions of these two ions together, and varying the ratios of one to the other (but keeping the volume constant), it is possible to remove the ions in varying proportions via the precipitate formed. By combing the two solutions, having them react, and measuring the conductivity of each solution, the least conductive of these solutions will have a stoichiometric ratio that is closest to the theoretical stoichiometric ratio for silver ions and the unknown ions. By analyzing the distribution of the data gathered, the most feasible of these stoichiometric ratios should fall somewhere between the most conductive, and second most conductive solution.

 

The experimental stoichiometric ratio for the silver ions and unknown ions is most likely to be 2:1, with a balanced equation of:

 

Possible source of error include:

  • Improper mixing of the solutions (resulting in heterogeneous mixtures, which could have different conductivities at different points)
  • Failure to rinse the conductivity sensor properly (which could cause it to obtain a false reading by mixing solutions together, or simply through reading the conductivity of whatever has not been removed.)
  • Failure to accurately measure the solution (which would disrupt the stoichiometric ratios within it, and thus the change the reaction, and the conductivity)
  • Human error is always in effect, given that the laboratory does not function under ideal conditions. As such, there is always the possibility of inaccuracies with measurement, perception of measurement, inaccuracies of equipment, and other such errors. (However, this is not likely to be the sole cause of the inaccuracies within this experiment, though it may contribute to it.)

 

Possible ways of improving the experiment on subsequent runs would include taking multiple measurements of the same solution (then averaging the results, to minimize the impact of false readings), making multiples of each solution (testing each, so as to improve sample size), and possibly trying to get a more sensitive sensor.

DRAFT: This module has unpublished changes.