064 – The influence of concentration on reaction rate 2

This protocol is centered on evaluating how the concentration of hydrochloric acid affects its reaction time with powdered magnesium and the resultant temperature changes.

Through this experimental setup, students will have the opportunity to delve into the principles of chemical kinetics, thermodynamics, and stoichiometry.

Educational Goals

  • Chemical kinetics: Gain an understanding of how the concentration of hydrochloric acid influences the speed of its reaction with magnesium, providing insights into reaction rates.
  • Thermodynamics: Observe and record the temperature changes during the reaction to identify its exothermic or endothermic nature, enhancing comprehension of energy changes in chemical processes.
  • Experimental skills: Develop precision in measuring liquids and solids and in monitoring chemical reactions, improving experimental technique and accuracy.
  • Analysis and interpretation: Learn to analyze time-based and thermal data to understand the impact of reactant concentration on the reaction, fostering analytical and interpretive skills in chemistry.

By investigating the effect of hydrochloric acid concentration on its reaction with magnesium, this experience offers valuable insights into the dynamics of chemical reactions.

Students will not only observe firsthand the influence of reactant concentration on reaction rate and temperature changes but also apply these observations to understand the interplay between chemical kinetics and thermodynamics. The skills and knowledge acquired through this laboratory are fundamental for designing chemical processes and for a deeper understanding of chemical reactions, preparing students for advanced studies and research in chemistry.

Protocol

Part 1 : reaction with 1M HCl

  1. Measure 100 mL of hydrochloric acid (HCl) 1M using the graduated cylinder.
  2. Pour the contents of the graduated cylinder into the calorimeter.
  3. Immerse the tip of the digital thermometer in the liquid to take its temperature.
  4. The initial temperature of the water will appear in the results table.
  5. Weigh approximately 0.4g of magnesium (Mg) powder.
  6. Pour the contents of the weighing boat into the calorimeter.
  7. Put the lid on the calorimeter.
  8. Insert the digital thermometer into the lid of the calorimeter.
  9. Start the stopwatch.
  10. Activate the green button of the agitator on the calorimeter lid.
  11. The graph of temperature as a function of time is on the tablet (graph tab).
  12. Note the final temperature when the reaction ends (at approximately 1 minute).
  13. Stop the stopwatch.
  14. The results are found in the results tab on the tablet.
  15. Stop the agitator by pressing the red button.
  16. Remove the thermometer from the calorimeter lid.
  17. Remove the calorimeter lid.
  18. Empty the contents of the calorimeter into the recovery tank.
  19. Rinse the calorimeter with distilled water and empty its contents into the recovery tank.
  20. Rinse the graduated cylinder with distilled water and empty its contents into the recovery tank.
  21. Reset the stopwatch.

Part 2 : reaction with 2M HCl

  1. Repeat steps 1 to 19 above but using hydrochloric acid (HCl) 2M.
  2. Note the time required until the end of the reaction, determined by the stabilization of the temperature. Compare to the reaction from part 1 performed with 1M hydrochloric acid (HCl).

Note : the reaction is accelerated 10 times faster, to more easily observe the complete reaction.

Anticipated Outcomes

Part 1

  • 0.42 g of Mg(s) powder will produce 440 kJ/mole of Mg.
  • In HCl 1 M, the temperature increase will be 17℃, in about 50 seconds.

Part 2

  • In HCl 2 M, the temperature increase will be 17℃, in about 22 seconds.

Summary of Assignment by Grade Range

Grades 3-5 (Ages 8-10)

  • Focus: Basic introduction to reaction rates, temperature changes, and concentration effects.
  • Activities: Observing reactions of powdered magnesium with hydrochloric acid at different concentrations, noting simple differences in reaction speed and temperature changes, basic safety instructions.

Grades 6-8 (Ages 11-13)

  • Focus: Intermediate understanding of reaction kinetics, thermodynamics, and concentration effects.
  • Activities: Conducting reactions with powdered magnesium and varying concentrations of hydrochloric acid, measuring temperature changes, observing how concentration affects reaction rate and temperature, following detailed safety protocols.

Grades 9-12 (Ages 14-18)

  • Focus: Advanced understanding of chemical kinetics, thermodynamics, and data analysis.
  • Activities: Accurately conducting reactions with powdered magnesium and different concentrations of hydrochloric acid, measuring and recording temperature changes and reaction times, analyzing the impact of reactant concentration on reaction rate and thermal changes, detailed recording and interpretation of results, adhering to advanced safety protocols, reinforcing concepts of chemical kinetics, thermodynamics, and stoichiometry.

Laboratory essentials

Instruments

  • Beaker (1000ml)
  • Calorimeter
  • Electronic scale
  • Graduated cylinders (70ml & 250ml)
  • Spatulas
  • Thermometers
  • Timer
  • Tweezers

Products

  • HCl 2 M (solution)
  • HCl 1 M (solution)
  • Magnesium (powder)
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