This experiment determines the stoichiometry of a reaction of magnesium and
HCl by measuring the pressure of the hydrogen gas produced using a PASCO Absolute
Pressure Sensor and a PASCO Science Workshop 500 computer interface. A constant amount of excess HCl is reacted with varying
amounts of magnesium solid. The change in pressure in a constant-volume (500-mL
Erlenmeyer flask) system is measured. The relationship between moles of magnesium
reacted and moles of hydrogen produced are plotted. The primary advantage of this
simple procedure is the opportunity for continuous interaction between the teacher,
students, and data as the data are being collected. Additional advantages are
that students can run several samples in a relatively short time (at least five
in a three-hour period) and can develop a real-time understanding of the relationship
between the amount of gas produced by a reaction and the pressure in the reaction
container. The experiment incorporates the use of technology, graphing, and spreadsheet
data analysis and is appropriate for either a general or introductory chemistry
laboratory.
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