This laboratory session is designed to quantify the volume of gas produced from the reaction between powdered magnesium and hydrochloric acid at varying concentrations. Through this procedure, students will delve into the principles of chemical stoichiometry, reaction kinetics, and the influence of reactant concentration on reaction speed.
Educational Goals
- Stoichiometry and Gas Production: Students will explore the stoichiometric relationships between solid reactants and gaseous products in chemical reactions, enhancing their understanding of mass-to-gas conversions.
- Chemical Kinetics Exploration: The experiment allows observation of how varying concentrations of hydrochloric acid influence the rate of gas production, providing a practical example of reaction kinetics.
- Experimental Technique Development: Participants will refine their skills in using laboratory equipment for measuring gas volumes, improving their experimental methodology.
- Data Interpretation Skills: Students will learn to analyze experimental results to derive insights into chemical kinetics laws, fostering their ability to understand and apply chemical principles.
By engaging in this laboratory, students gain practical insights into the impact of reagent concentration on the speed of chemical reactions. They learn to accurately measure gas production during a reaction and analyze how different variables affect this process. Experience reinforces the importance of precise experimental practices and data analysis in understanding fundamental chemistry principles, equipping students with the skills necessary for conducting experimental research.
Protocol
Part 1: Gas burette setup
a) Fill a 1-liter beaker with 800 mL of tap water.
b) Position this beaker next to the stand.
c) Install a universal clamp above the center of the beaker to support the gas burette.
d) Fill the gas burette with water.
e) While holding the burette upside down, block its opening with your thumb.
f) Place the inverted gas burette in the clamp, ensuring its opening is close to the bottom of the beaker.
g) Gently release your thumb to allow the burette to be immersed without losing water.
h) Adjust the setup if necessary to prevent water loss from the burette.
i) Attach a “J” shaped plastic connector under the opening of the gas burette.
Part 2: Reaction preparation
j) Measure 100 mL of 0.5 M hydrochloric acid (HCl) and pour into an Erlenmeyer flask.
k) Place the weighing boat on the balance scale and press tare to zero out.
l) Weigh the desired amount of magnesium powder (Mg) – about 0.2 g.
m) Insert the magnetic stirrer into the Erlenmeyer.
n) Start the stopwatch by pressing the red button.
o) Add the magnesium to the Erlenmeyer, then seal with a stopper fitted with a glass elbow.
p) Connect the rubber tube to the glass elbow and to the Erlenmeyer stopper, and place the Erlenmeyer on the heating plate without turning it on.
q) Activate the stirrer by pressing the button on the heating plate.
Part 3: Starting the reaction and data collection
r) Observe the formation of gas bubbles and their rise in the burette.
s) Note the volume of dihydrogen gas (H2) collected after the end of the reaction (about 245 seconds).
t) Empty the glassware contents into the recycling bin and clean with distilled water.
Part 4: Analysis of results and comparisons
u) Data on the amount of dihydrogen formed over time will be accessible via a graph in the tablet’s graph tab.
v) Repeat the previous steps for hydrochloric acid concentrations of 1M and 2M, and compare the reaction times.
** Note: the reaction is accelerated 2 times faster to more easily observe the complete reaction.
Anticipated Outcomes
Using approx. 0,2 g of Magnesium and 100 mL of 0.5M HCl, the reaction should take approx. 468 seconds (234 secs accelerated x2), and the volume of H2 produced should be approx. 212 mL.
At 1 M HCl, the reaction should take approx. 212 seconds (106 secs accelerated x2). At 2 M HCl, the reaction should take approx. 100 seconds (50 secs accelerated x2).
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to reaction rates and gas production concepts.
- Activities: Observing gas production from reactions of powdered magnesium with different concentrations of hydrochloric acid, simple discussions on how concentration affects reaction speed, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding of stoichiometry, reaction kinetics, and gas production.
- Activities: Conducting reactions with powdered magnesium and varying concentrations of hydrochloric acid, measuring the volume of gas produced, observing how concentration affects reaction rate, following detailed safety protocols.
Grades 9-12 (Ages 14-18)
- Focus: Advanced understanding of stoichiometry, reaction kinetics, and data interpretation.
- Activities: Accurately conducting reactions with powdered magnesium and different concentrations of hydrochloric acid, measuring and recording the volume of gas produced, analyzing the impact of reactant concentration on reaction rate, detailed recording and interpretation of results, adhering to advanced safety protocols, reinforcing concepts of chemical kinetics and stoichiometry.
Laboratory essentials
Instruments
Beaker (500 ml, 1000 ml)
Electronic scale
Elbow holed cap
Erlenmeyer (250 ml)
Gaz burette
Graduated cylinders (250 ml)
Hot plate
Lab Stand & Clamps
Magnetic stirrer
Plastic connector
Spatula
Thermometers
Timer
Products
HCl 0.5M (solution)
HCl 1.0M (solution)
HCl 2.0M (solution)
Magnesium (powder)