Evaluation of a Gas Constant (Experiment)

Experiment 3: Evaluation of Gas Constant

Purpose:

The purpose of this lab is to demonstrate the ideal gas law under ordinary conditions. In this lab, the variables in the ideal gas law are known or can be found aside from the constant R. Thus, the R values can be found and relatively determine the relevancy of the ideal gas law to the lab conditions. The ideal gas law was tested using the reaction:

Mg (s) + 2HCl2 (aq) H2 (g)

Procedure:

Ribbons of magnesium (5) were cut to the approximate length of the instructor’s example and were weighed separately on scale #1.

HCl provided by the instructor was added to a eudiometer tube (8mL). The rest of the tube was filled with water. One of the magnesium tapes was wrapped around a piece of copper wire in the opening of the tube. The eudiometer tube was then inverted over and into a 450 mL beaker with water. The initial volume was recorded. While the reaction occurred, the temperature was taken at 1 minute intervals for 3 minutes.

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After the reaction occurred, the height difference from the solution within the eudiometer tube and the top of the liquid volume in the beaker was recorded. The final volume was also recorded.

Summary Table:

• Mean of R= .0737
• Standard Deviation= .0298
• Relative Standard Deviation= 40.46%
• Summary Table:
• Mean of R= .0737
• Standard Deviation= .0298
• Relative Standard Deviation= 40.46%

Discussion:

This lab was supposed to generate numbers close to the R constant by plugging in the values acquired in reaction Magnesium and Hydrochloric acid reaction. (The reaction results in H2 gas.

) The mean acquired from our data set was .0737 L-ATM/mol-K as opposed to the actual constant .08206 L-ATM/mol-K. The constant we acquired was much lower in value, potentially due to the outlier in our data set: Trial Four. Trial Four resulted in the R value .0205 ATM-L/K-mol which skewed our relative mean, standard deviation and relative standard deviation. By removing the fourth trial from the data set, the new mean is .08705 L-ATM/mol-K, a closer but slightly higher R value. The standard deviation would be .00236 and the relative standard deviation would be 2.71%. These values have more precision than the 40.46% relative standard deviation and .0298 standard deviation acquired in the entire data set. I believe there must have been an error in the methodology to produce the outlier result in the fourth trial. Too much liquid could have been spilled during the process or perhaps the magnesium did not fully react because it was so tightly bound around the copper. The error in this lab could range from those listed above and inaccurate measurements.