Gas stochiometry:

prelab assignment (10 points) due at the begining of lab

• describe how to determine the mass of Mg in the following chemical reaction
  Mg _(s)  +  (excess) HCl _(aq) -->  H_{2 (g)}  +  MgCl_{2 (aq)}
  based on the experimental measurements (related to H₂ ); include all formulas in analysis.
• sketch a data table for your experimental measurements (to accomplish the goals of this lab - see its purpose)
• view the video on the effect of acid on protein, e.g. your eyes

purpose

compare the actual mass of Mg to the experimentally determined mass of Mg (in the above reaction)

materials

~15 mm Mg ribbon, ~ 20 mL 6 M HCl, water

eudiometer tube (measures the volume of a gas), thermometer, barometer, 2-hole stopper

beaker, ruler, thread (to secure Mg to stopper); balance

methods / data analysis

student design

Content of lab report [30 points]

introduction  [5 points]:  describe the calculations using equation / formula (); do not use actual values

experimental methods  [5 points]

data analysis  [15 points] : 

• calculation to determine the mass of Mg based on measurements related to H₂ gas & % error; show calculations & data table
• statistics (include interpretation of p-value; refer to the purpose of the lab)
• calculate % error (recomend use MS Excel; may refer to it rather than showing calculations) due to:
  • not correcting for water vapor
  • not correcting for the height of the column of water in the eudiometer tube
  • not correcting for both of the preceding factors

discussion  [5 points]

• what is the importance to correct for the preceding factors ?  i.e. consequence for NOT correcting for these factors ?
• provide a plausible, nontrivial error (not the preceding factors) to rationalize your results. be specific.

 

additional resources

table relating the partial pressure of water as a function of temperature

lab activity source (examples):  site 1  &  site 2  [access 4 / 2009