Reaction rate and Particle Size

Title: Investigating the Effect of Particle Size on Reaction Rate: Dissolution of Calcium Carbonate in Hydrochloric Acid

Aim: To investigate how the particle size of calcium carbonate affects the rate of reaction with 2 Molar Hydrochloric Acid.

Materials:

1. Calcium carbonate (marble chips)
2. 2 Molar Hydrochloric Acid
3. Stopwatch or timer
4. Dropper bottles containing 2 Molar Hydrochloric Acid
5. Test tubes
6. Safety glasses

Method:

1. Ensure all students wear safety glasses throughout the experiment to ensure safety.
2. Measure out equal amounts ~0.5g of calcium carbonate in both powdered and chip forms
3. Label two separate test tubes as “Powdered Calcium Carbonate” and “Chip Calcium Carbonate” and place them in a rack.
4. Start the stopwatch or timer.
5. Add the pre-measured calcium carbonate samples to their respective test tubes
6. Using the dropper bottles, dispense 5 mL of 2 Molar Hydrochloric Acid into each labelled test tube.
7. Stir each mixture gently and consistently to ensure thorough mixing.
8. Observe and record any visible changes in each reaction mixture, such as the release of gas bubbles or changes in color.
9. Monitor the reactions until the calcium carbonate has fully dissolved or stopped bubbling in each test tube.
10. Stop the stopwatch or timer when the reaction is complete.
11. Carefully dispose of the reaction mixtures down the sink with plenty of water, following proper laboratory procedures for chemical waste disposal.
12. Repeat the experiment at least two more times to ensure reliability of results.
13. Calculate the average time taken for each type of calcium carbonate (powdered and chip) to fully react with the hydrochloric acid.
14. Analyse the data and draw conclusions regarding the effect of particle size on the rate of reaction.

Safety Precautions:

1. Handle hydrochloric acid with care and avoid contact with skin, eyes, and clothing. In case of contact, rinse immediately with water and seek medical attention if irritation persists.
2. Work in a well-ventilated area or under a fume hood to prevent inhalation of fumes.
3. Do not inhale or ingest calcium carbonate or hydrochloric acid.
4. Ensure proper disposal of chemical waste according to laboratory safety guidelines.

Discussion:

1. Based on your results, how did the particle size of calcium carbonate affect the rate of reaction with hydrochloric acid? Was there a noticeable difference in reaction rate between the two particle sizes?
2. Were there any unexpected results or inconsistencies in your data? If so, what might have caused these variations?
3. Can you explain why particle size might influence the rate of reaction? How does surface area-to-volume ratio play a role in this process?