Chemical Kinetics Roshini Ramachandran Learning Outcomes Students - PowerPoint PPT Presentation

Chemical Kinetics Roshini Ramachandran

Learning Outcomes Students will be able to: 1. Predict the effect of reaction temperature on the rate of a chemical reaction. 2. Interpret a graph plotted between rate of a chemical reaction and temperature 3. Discuss the application of chemical kinetics in certain biological systems 4. Distinguish between the factors affecting rate and rate constant

Topics covered to date Students have learned: 1. Rates, Rate Constants, Order of reactions 2. Differential and Integrated Rate Laws 3. Activation Energy & Arhennius ’ Equation 4. Effect of reactant concentration on rate

Recap: Effect of concentration Red dye + bleach  Colorless product Rate = -d[dye]/dt = k[dye] m [bleach] n INSERT CLICKER QUESTION ON THE EFFECT OF REACTANT CONCENTRATION ON THE RATE OF A CHEMICAL REACTION

Effect of temperature

Clicker Question Increasing the temperature of a reaction increases its reaction rate. A) Yes B) No C) Cannot say

Case Study Worksheet: Class Discussion INSERT IMAGE OF NEWS ARTICLE/TITLE FROM https://www.cbsnews.com/news/florida-frozen- iguanas-falling-from-trees-during-cold-snap-bomb- cyclone-storm-east-coast/ INSERT IMAGE OF NEWS ARTICLE/TITLE FROM https://www.cbsnews.com/news/effort-to-save-cold- stunned-sea-turtles-cold-weather/

Cold-blooded animals & temperature Thermal Image of reptile INSERT THERMAL IMAGE OF LIZARD FROM http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/lizard.html (I use http://coolcosmos.ipac.caltech.edu/image_galleries/ir_zoo/images/lizard3_ir.jpg) Body temperature depends on surroundings

Case Study Worksheet: Class Discussion Food for thought: Identify one potential method to save these animals (Discuss in your groups)

Recap: Collision Theory It is only collisions that possess at least the activation energy for the reaction which result in a reaction IMAGE OF THERMALLY ENERGETIC IMAGE OF BOLTZMANN DISTRIBUTION COLLISIONS OF MOLECULAR ENERGIES Recommended: Figure 14.14, pg. 608 Recommended: Figure 14.15, pg. 611 Tro NJ, Fridgen T, Shaw L. 2010. Tro NJ, Fridgen T, Shaw L. 2010. Chemistry: A Molecular Approach, Chemistry: A Molecular Approach, 2nd US edition. Pearson. 2nd US edition. Pearson. Image credit: Tro NJ, Fridgen T, Shaw L. 2010. Chemistry: A Molecular Approach, 2nd US edition. Pearson.

Rate and Rate constant Arhennius Equation: k = Ae – Ea/RT Factors affecting rate constant? Ans: Temperature Factors affecting rate? Ans: Concentration, Temperature

Catalysts • Alters the rate of a reaction by providing an alternate pathway with lower activation energy. • Participates in a reaction by forming an intermediate, but is regenerated. NO (catalyst) IMAGE OF REACTION ENERGY 2SO 2 + O 2  2SO 3 DIAGRAM FOR A CHEMICAL REACTION WITH A CATALYST Mechanism: 2NO + O 2  2NO 2 Recommended: Figure 14.17, pg. 619 i. NO 2 + SO 2  SO 3 + NO ii. Tro NJ, Fridgen T, Shaw L. 2010. Chemistry: A Molecular Approach, 2nd US edition. Pearson.

Enzymes • Enzymes are biological catalysts that enhance reaction rates. • Almost all enzymes are proteins, and contain active sites that can bind to a substrate. • They are highly specific to their substrates and catalyze only one type of chemical reaction. IMAGE OF ENZYME-SUBSTRATE BINDING Recommended: Figure 14.21, pg. 622 Tro NJ, Fridgen T, Shaw L. 2010. Chemistry: A Molecular Approach, 2nd US edition. Pearson.

Effect of temperature on enzymatic reactions IMAGE OF EFFECT OF TEMPERATURE ON AN ENZYME CATALYZED REACTION VS SIMPLE CHEMICAL REACTION http://www.bbc.co.uk/staticarchive/199acbfe2bac854818 d719d6ce0e53e4cd3cd5d2.gif Enzyme denaturation occurs at higher temperatures