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Bhopal - Rate of Reaction

Written for PULSE by Christopher Martin
Edited By: Stephanie Nardei



Time: 1 class period
Preparation
Time:

20 minutes to print articles for students and load PowerPoint

Materials: Internet Access

Abstract
On December 3rd, 1984, 8000 people died when the chemical plant in Bhopal blew up. Students will follow directions and do labs that investigate factors that affect the rate of reaction.

Objectives
Students will be able to:

  • Relate that the rate of reaction is affected by temperature, surface area, concentration of reagent, and addition of a catalyst or inhibitor.

National Science Education Standard
The Physical Setting

D. The structure of Matter  
9, The rate of reactions among atoms and molecules depends on how often they encounter one another, which is affected by the concentration, pressure, and temperature of the reacting materials.

Arizona Science Standard
Strand 5: Physical Science
Concept 4: Chemical Reactions
Investigate relationships between reactants and products in chemical reactions.
PO.11
Predict the effect of various factors (e.g., temperature, concentration, pressure, catalyst) on the equilibrium state and on the rates of chemical reaction.

Teacher Background
In 1970, Union Carbide decided to manufacture in Bhopal the environmentally-sound pesticide, Sevin. Discovered in 1957, Sevin was proven to decrease the damage of crops due to insects by fifty percent without the harmful ecological effects of DDT and other insecticides.

On December 3, 1984, a cloud of toxic methyl isocyanate (MIC) drifted through Bhopal, India, killing thousands of the city’s destitute residents. Water entered a storage tank of MIC at the pesticide-producing plant, causing a massive exothermic reaction and the release of thousands of tons of lethal MIC gas. The revered economic center of Bhopal became the epicenter of the disaster that destroyed the city.

The Bhopal catastrophe was a reactive incident involving inadvertent mixing of incompatible chemicals, a runaway decomposition reaction, and a devastating toxic gas release. In these lessons, students will learn about the Bhopal disaster, learn about the chemistry of the reaction and understand how reaction rates are controlled.


Related and Resource Websites
Bhopal Information Center: http://www.bhopal.com/
Bhopal Disaster on Wikipedia http://en.wikipedia.org/wiki/Bhopal_Disaster (image taken from here)
International Campaign for Justice in Bhopal http://www.bhopal.net/
The Bhopal Medical Appeal http://www.bhopal.org/
Blogs on Bhopal http://www.bhopal.org/blogs.html
The Bhopal Chemical Disaster http://www.pitt.edu/~lalanne/event.html
Answers.com on Methyl-isocyanate http://www.answers.com/topic/methyl-isocyanate
TED Case Studies on Bhopal http://www.american.edu/ted/bhopal.htm

 

 

stoichiometry

Activity

  1. Place a sugar cube into a beaker of cold water and let students observe the cube dissolve.
  2. Ask students how they could increase the rate of reaction; dissolving the sugar in the water. Answers may include stirring, heating it up and crushing the sugar cube into powder.
  3. Explains that increasing the temperature makes the molecules move faster and does affect the rate of reaction; and, crushing the sugar cube will increase the surface area.
  4. Take a piece of magnesium ribbon and puts it into a beaker of 0.1molar Hydrochloric acid. The students observe that the reaction rate is slow. Students should discuss how the reaction rate can be increased.
  5. Explain that by using a stronger acid, a more concentrated acid, the reaction rate can be altered. In some reactions, a catalyst or inhibitor can be used. They work by changing the activation energy.
  6. Students will read the reaction rate lab, make predictions and do the four labs that illustrate the four factors affecting reaction rate.

Factoring affecting the rate of reaction

Temperature
Surface area
Concentration of reagents
Catalyst or inhibitor

Predictions
Increasing the temperature will increase/decrease the rate of reaction.

Increasing the concentration of the reagents will increase/decrease the rate of reaction.

Increasing the surface area of the reagent will increase/decrease the rate of reaction.

Adding a catalyst will decrease the activation energy. This will increase/ decrease the rate of reaction.

Adding an inhibitor will increase the activation energy. This will increase/ decrease the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the temperature.

Method
Pour 200 ml of water into a beaker. Record the temperature. Add an antacid tablet to the water and record the time that it takes to dissolve. Heat 200 ml of water. Record the temperature. Add an antacid tablet to the hot water and record the time that it takes to dissolve.

Results

Temperature of water

Time taken to dissolve

 

 

 

 

Conclusion

Temperature increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the surface area.
Method

Pour 200 ml of water into a beaker. Add an antacid tablet to the water and record the time that it takes to dissolve. Use a pestle and mortar to crush an antacid tablet. Add the powder to a second 200 ml. of water and record the time taken to dissolve.

Time taken to dissolve

Tablet

 

Powder

 

Conclusion

Increasing the surface area increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of increasing the concentration of reagent

Method
Wear goggles. Cut a strip of Magnesium ribbon 2cm long. Use a measuring cylinder to measure 50ml. of 2molar Hydrochloric acid. Add the Mg ribbon to the acid and record the reaction time. Prepare 1M, 0.5M and 0.2M solutions of hydrochloric acid by dilution and measure the reaction time with the dilute acids.

Molarity of HCl

2M HCl

Water

1M

25ml

25ml.

0.5M

12.5ml.

37.5ml

0.2M

5ml.

45ml.

Results

Concentration of HCl

Reaction Time

2 Molar

 

1 Molar

 

0.5 Molar

 

0.2 Molar

 

Graph your results with concentration on the X axis and reaction time on the Y axis. Use graph paper. Write a balanced chemical equation for the reaction.

Conclusion
Increasing the surface area increases/ decreases the rate of reaction.

LAB: To determine the affect on rate of reaction of using a catalyst

Method
Pour 20 ml of Hydrogen peroxide into a boiling tube. Record your observations. Add a small amount of Manganese dioxide and record your observations

Observation

Hydrogen Peroxide

 

Hydrogen Peroxide + Manganese dioxide

 

Balance the equation
H2O2 à H2 + H20

Conclusion
Adding a catalyst increases/ decreases the rate of reaction.

bonusEarn Extra Credit

Define activation energy and draw a diagram to explain how a catalyst will affect the activation energy. Find out how Graphite is used as an inhibitor in a nuclear power station.

Homework
Students should review what they learned.

Embedded Assessment
Completion of the experiments and correct conclusions based on individual results will indicate understanding.

 

 

 


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:


an
NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award

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LOGO - NIEHS Center LOGO - NIEHS

Supported by NIEHS grant # ES06694


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