CHEM 1212 Exam 2 Review Presented by UGA’s Academic Resource Center 02/28/16

Chapter 14: Chemical Kinetics

Relative Rates Example of instantaneous rate In terms of reactants In terms of products

Which of the following will not usually increase the rate of a chemical reaction? A.Crushing a solid reactant B.Decreasing the concentration of a reactant C.Increasing the temperature D.Liquefying a reactant

Why should one expect an increase in temperature to increase the initial rate of reaction? Why should one expect a gaseous state reaction to happen faster than a solid state one? Is the activation energy of the gaseous reaction higher or lower than the solid state?

What affects reaction rate? Temperature – Increased temperature  Increased rate Surface Area – Increased surface area  Increased rate Catalysts – Accelerate reaction by lowering the activation energy barrier, but are not consumed Concentration – As demonstrated by rate law

Rate Law Expression Order Rate Constant Units k is a proportionality (rate) constant for a given reaction at a certain temperature

What’s a pseudo-first order reaction?

A + 2B  3C Experiment[A] (mol/L)[B] (mol/L)Initial Rate (mol/L·s) × × × Experiment[A] (mol/L)[B] (mol/L)Rate of Formation of C (mol/L·s) × × × What’s the difference in the approach to these two determinations?

Zeroth Order Integrated Rate Law

First Order Integrated Rate Law

Second Order Integrated Rate Law

Collision Theory 1.The reacting molecules must collide with one another. 2.The reacting molecules must collide with sufficient energy to initiate the process of breaking and forming bonds. 3.The molecules must collide in an orientation that can lead to rearrangement of the atoms and the formation of products.

Collision Theory 1.The reacting molecules must collide with one another. 2.The reacting molecules must collide with sufficient energy to initiate the process of breaking and forming bonds. 3.The molecules must collide in an orientation that can lead to rearrangement of the atoms and the formation of products.

Reaction Coordinate Diagram

Collision Theory 1.The reacting molecules must collide with one another. 2.The reacting molecules must collide with sufficient energy to initiate the process of breaking and forming bonds. 3.The molecules must collide in an orientation that can lead to rearrangement of the atoms and the formation of products.

The Arrhenius Equation

Although an increase in temperature results in an increase in kinetic energy, this increase in kinetic energy is not sufficient to explain the relationship between temperature and reaction rates. How does the activation energy relate to the chemical kinetics of a reaction? Why does an increase in temperature increase the reaction rate despite the fact that the average kinetic energy is still less than the activation energy?

Mechanisms NO 2 + CO  NO + CO 2 1.2NO 2  NO 3 + NO (slow) 2.NO 3 + CO  NO 2 + CO 2 (fast)

Break for Questions

Chapter 15: Equilibria

Equilibrium Constant EquationH 2 (g)I 2 (g)2 HI(g) Initial (M) Change (M) Final (M)

Magnitude of K K > 1 – Product favored – Add to products, subtract from reactants K < 1 – Reactant favored – Add to reactants, subtract from products

Reaction Quotient Q < K – Reactants  products Q = K – Reaction at equilibrium Q > K – Reactants  products

Stoichiometry of K

Break for Questions