Introduction:

Equipment:

• Data Collection System
• Absolute Pressure Sensor with Quick Release, Connectors, and Plastic Tubing
• Stainless Steel Temperature Sensor
• Stand, with Clamp
• Graduated Cylinder, 25-mL
• Graduated Cylinder, 250-mL
• Erlenmeyer Flask, 250-mL
• Beaker, 1500-mL
• Balance
• 3 M HCl, 100 mL
• Unknown Metal, 0.2g
• Electrical Tape

Method:

• Gathered all equipment and materials. Inspected all equipment for damage or contamination.
• Set up Data Collection System, assembled GLX, pressure sensor, associated tubing, with stopper, and temperature sensor.
• Measured the volume of the Erlenmeyer flask, by filling it with water, then pouring the contents into the graduated cylinder. Dried flask.
• Wrapped the Erlenmeyer flask with the electrical tape.
• Filled 1500-mL beaker with 1125 mL of water, and placed beneath stand. Placed temperature sensor in water bath.
• Mounted the Erlenmeyer flask on the stand, ensuring that as much of it is immersed as possible within the bath.
• Measured between 0.150 g and 0.180 g of the unknown metal.
• Measured 20.0 mL of 3.0 M HCl, and placed it in the Erlenmeyer flask.
• Covered with Stopper and associated tubing, then measured base atmospheric pressure.
• Removed stopper, and added metal to Erlenmeyer flask. Resealed flask.
• Measured the shift in pressure with the reaction, stopped measurements once pressure leveled off, then repeated the process three more times, for more accurate results.
• Disposed of solutions in designated containers. Cleaned all glassware, set them to dry in their designated areas, and returned all equipment to its point of origin.

Data Analysis:

Average Experimental Formula Weights:

• Trial 1: 219.432 grams per mole
• Trial 2: 438.865 grams per mole
• Trial 3: 658.298 grams per mole

Due to significant error within the experiment, no conclusive findings could be reached. See conclusion for a discussion of error.

Formulas used:

Conclusion:

The goal of this experiment is to learn how to identify an unknown metal element, by reacting it with an acid. By reacting metals with a more negative reduction potential than hydrogen ions, it can reduce them to diatomic hydrogen gas. This means that when such a metal (of known mass) is reacted with an acid, one can collect the hydrogen gas released, in a container of known volume and temperature, and calculate the number of moles of hydrogen via the ideal gas law formula:

 Given that one would then know the amount of hydrogen released by the reaction, and the acid used, one could then calculate how many moles of acid was used, and then from that, potential stochiometric ratios of the metal. Given that one had measured the mass, and now knows the number of moles (potentially, given possible stoichiometric differences), and that moles are equal to grams divided by the formula weight of the element, one could then calculate the possible formula weight via the equation:

 The various stoichiometries can then be tested via this equation, and the result cross referenced against the periodic tables, and thus be used to determine which element was the unknown metal.

Average Experimental Formula Weights:

• Trial 1: 219.432 grams per mole
• Trial 2: 438.865 grams per mole
• Trial 3: 658.298 grams per mole

No calculation of error is possible, though based on the experimental formula weight, it is readily apparent that there was a significant source of error within our experiment.

Possible sources of error include:

• Failure to properly seal the Erlenmeyer flask, thus allowing air to escape, disrupting the measurement of pressure.
• Failure to properly attach to the pressure sensor's tubing, also introducing the possibility of leaks. 
• Any defects with the GLX system or its sensors. Improper setup could also cause error.
• Failure to properly measure the volume of the Erlenmeyer flask, thus disrupting subsequent calculations.
• Failure to properly measure the mass of the unknown, or the volume (or molarity) of the HCl.
• Contamination of HCl solution, or unknown metal sample.
• Failure to properly maintain the temperature of the experiment, thus changing the pressure.
• Failure to react all of the unknown metal, thus failing to produce the expected amount of hydrogen gas, and disrupting all subsequent calculations.
• 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 improvements that one could make to the experiment include using more accurate sensors, using containers that are less likely to leak, testing all measurements to ensure that they were performed properly, adding some means by which to test the seal of the Erlenmeyer flask, ensuring that I and my lab partners read the experiment beforehand (increasing familiarity with the procedure, and minimizing human error), checking to see that all data has been properly distributed among all lab partners in a timely manner, and repeating the experiment multiple times (to minimize the impact of an anomalous result).