HomeClass Notes1,200,000CA670,000

CHEM 120 Lecture Notes - Lecture 7: Kinetic Theory Of Gases, Collision Theory, Activated Complex

46 views4 pages

10 Feb 2016

School

McGill University

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

cudapuca and 38677 others unlocked

CHEM 120 Full Course Notes

CHEM 120 Full Course Notes

Document Summary

Chem 120 lecture 7 collision theory & reaction mechanisms. 14. 8: theoretical models for chemical kinetics: collision theory. Kinetic- molecular theory can be used to calculate the collision frequency of a gas: in gases at stp, ~10^30 collisions occur per second in 1l! huge! If each reaction proceeded at that rate/if each collision produced a reaction, then the rate would be huge! ~10^30/na: actual rates in gas reactions are generally much slower a typical value being. 10^-4m/s thus only a small fraction of collisions produce a reaction. Not all collisions result in a chemical reaction (ie. only collisions between molecules whose combines ke is above the minimum will react) For a reaction to happen, there must be a redistribution of energy sufficient to. Activation energy (ea) = the minimum ke that molecules need to bring to their collisions for a chemical reaction to occur. Kinetic energy distribution: (only some particles react. Shaded area is proportional to e-ea/rt, therefore dependent on temperature.

Related textbook solutions

Chemistry: Structure and Properties

ISBN: 9780134293936

Basic Chemistry

ISBN: 9780134138046

Principles of Chemistry Molecular Approach

ISBN: 9780134112831

Chemistry: Structure and Properties

ISBN: 9780134293936

Principles of Chemistry Molecular Approach

3rd Edition, 2014

ISBN: 9780321971944

Chemistry: A Molecular Approach

ISBN: 9780321809247

Chemistry: A Molecular Approach

ISBN: 9780134874371

Principles of Chemistry: A Molecular Approach

ISBN: 9780134895741

Chemistry: The Central Science

14th Edition, 2017

ISBN: 9780134414232

Related Documents

CHEM 120 Lecture Notes - Lecture 7: Gas Constant, Collision Theory, Activation Energy

periwinkletortoise498

CHEM 120 Lecture Notes - Lecture 10: Transition State Theory, Inverse Relation, Collision Theory

CHEM 120 Lecture Notes - Lecture 14: Activated Complex, Chemical Potential, Iodine Monochloride

salmontortoise330

Related Questions

Chemical reactions occur when molecules or atoms collide, the bondsbetween atoms are broken, and new bonds are formed. Breaking thebonds of the reactants requires energy; bond formation releasesenergy. Which of the following statements regarding energy changesduring a reaction are true?
(A)The activation energy (Ea) of the forward reaction is thedifference between the energy of the products and the energy of thetransition state.
(B)If the heat of reaction, ?H, is positive, the energy of theproducts is lower than the energy of the reactants, and thereaction is endothermic.
(C)When the activation energy is low, the reaction rate isslow.
(D)Two or more atoms must collide, with proper orientation, withenergy greater than or equal to the activation energy for areaction to occur.
(E)Increasing the concentration of reactants increases the numberof collisions, and the reaction goes faster.
(F)The energy of a collision between atoms or molecules must begreater than the activation energy (Ea) for bonds to bebroken.
(G)Decreasing the temperature decreases the kinetic energy of thereactants, and the reaction goes more slowly.

Help with these

In the collision model it is assumed that reactions occur as a result of collisions between molecules with the correct kinetic energy and orientation. The minimum energy required for a reaction to occur when molecules collide is called the activation energy, E_a. The number of collisions that are favorably oriented for a reaction is described by the frequency factor, A. The Arrhenius equation relates both of these factors to the rate constant, k. k = A middot e^-E_a/(R middot T) where R = 8.314 J/(mol middot K) and T is the temperature in kelvins. Based on the activation energies and frequency factors, rank the following reactions from fastest to slowest reaction rate, assuming they are all at the same temperature. Rank from fastest to slowest reaction rate. To rank items as equivalent, overlap them. Fraction of molecules The exponential term in the Arrhenius equation is equal to the fraction of molecules, f, with kinetic energy greater than or equal to the activation energy: f = e^-E_a/(R middot T) Most scientific calculators have an e^x function as the second function of the LN button. Part B A certain reaction with an activation energy of 145 kJ/mol was run at 495 K and again at 515 K. What is the ratio of f at the higher temperature to f at the lower temperature? Express your answer numerically using one significant figure. In the collision model it is assumed that reactions occur as a result of collisions between molecules with the correct kinetic energy and orientation. The minimum energy required for a reaction to occur when molecules collide is called the activation energy, E_a. The number of collisions that are favorably oriented for a reaction is described by the frequency factor, A. The Arrhenius equation relates both of these factors to the rate constant, k: k = A middot e^-E_a/(R middot T) where R = 8.314 J/(mol middot K) and T is the temperature in kelvins. Part A Based on the activation energies and frequency factors, rank the following reactions from fastest to slowest reaction rate, assuming they are all at the same temperature. Rank from fastest to slowest reaction rate. To rank items as equivalent, overlap them. Fraction of molecules The exponential term in the Arrhenius equation is equal to the fraction of molecules, f, with kinetic energy greater than or equal to the activation energy: f = e^E_a/(R middot T) Most scientific calculators have an e^x function as the second function of the LN button. Part B A certain reaction with an activation energy of 145 kJ/mol was run at 495 K and again at 515 K. What is the ratio of f at the higher temperature to f at the lower temperature? Express your answer numerically using one significant figure. In the collision model it is assumed that reactions occur as a result of collisions between molecules with the correct kinetic energy and orientation. The minimum energy required for a reaction to occur when molecules collide is called the activation energy, Ea. The number of collisions that are favorably oriented for a reaction is described by the frequency factor, A. The Arrhenius equation relates both of these factors to the rate constant, k: k = A middot e^-E_a/(R middot T) where R = 8.314 J/(mol middot K) and T is the temperature in kelvins. Fraction of molecules The exponential term in the Arrhenius equation is equal to the fraction of molecules, f, with kinetic energy greater than or equal to the activation energy: f = e^-E_a/(R middot T) Most scientific calculators have an e^x function as the second function of the LN button. Part B A certain reaction with an activation energy of 14 kJ/mol was run at 495 K and again at 515 K. What is the ratio of f at the higher temperature to f at the lower temperature? Express your answer numerically using one significant figure.