unknown metal - Purpose: Identification of an unknown metal...

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Purpose: Identification of an unknown metal sample, this unknown metal sample will be reacted with a strong aqueous acid; this will result in gas production. Collecting the sample of gas will take place over water and then using the Ideal Gas Law and stoichiometry to calculate the moles of the metal, and then the mass and from that the molar mass, this will provide a basis for the identification of the unknown metal. Procedure: Obtain a 1L beaker and fill ~three quarters of the way fill with tap water, then fill a 50ml graduated cylinder as full as possible with tap water. Being very careful not to spill any water cover the top of the graduated cylinder with a glove and invert it quickly into the 1L beaker. Remove the glove after submerging the graduated cylinder. Clamp the cylinder in place in the inverted position. Continue construction of the apparatus by threading the rubber tubing of the pre-assembled stopper/gas delivery system under the water line, and into the mouth of the inverted graduated cylinder. The J part of the tube should be far enough into the cylinder to ensure that it will not come out while gas is being collected. Choose one of the three unknown metals and weight. Place the metal in the bottom of the test tube making sure it is not touching the sides of the test tube. Carefully obtain a half to two-thirds filled vial of 6.00M HCL and slowly slide it down the side of the test tube it should be sitting on top of the metal. This needs to be done without spilling any of the acid. Place the rubber stopper on securely. Now check with T/A to make sure the apparatus is assembled properly. Obtain temperature ( C) and the atmospheric pressure (torr) and then convert so the R-constant 0.08206 L atm/mol K can be used. If some air was allowed into the graduated cylinder in the process of inverting it into the beaker, take a reading of this initial volume of trapped air (V initial ). (V final – V initial ) subtracts this initial volume out after the gas collection is complete. To begin gas collection make sure rubber stopper is very secure and tilt the test tube slightly so the HCL pours out of the small vial, making sure the test tube is not inverted to allow the HCL to come in contact with the rubber stopper. Gas evolution commences at once, this process may take several minutes, but the entire metal sample must be completely dissolved. Before taking final volume measurement make sure, the water level is the same inside and outside the graduated cylinder, adjusting by hand. Repeat this procedure three times, three trials. When finished with each of the three trials pour the remaining HCL in the 1L beaker stirring to
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This note was uploaded on 01/30/2012 for the course CHEMISTRY 212 taught by Professor Ha during the Spring '11 term at George Mason.

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unknown metal - Purpose: Identification of an unknown metal...

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