1nd CHEM 1200 Edition Lecture 6 Outline of Last Lecture I Method of initial Rates a How to calculate Rate order i Rate 2 Rate 1 A n x B m x C p for rate 2 A n x B m x C p for rate 1 II Concentration and Time a Zeroth Order reaction b First Order reaction c Logarithm Review d Confirming First Order Reactions e Second Order Reactions Outline of Current Lecture I II III Half Life a Equations for each order How can we control the rate of a chemical reaction Temperature and Rate a Collision Model b Activation Energy c Arrhenius Equation Current Lecture I Half Life a Half life t1 2 the time required for the concentration of a reactant to decrease to one half its initial value i After one half life A A initially b First Order Reactions after one half life ln 2 k These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III i Independent of A initially ii Constant c Second Order Reactions i 1 k A initially After one half life ii Is not constant half life gets larger d Zeroth Order Reactions A initially 2k i Is not constant half life gets smaller How can we control the rate of a chemical reaction a Concentration molecules must collide to react b Physical state molecules must mix to collide c Temperature molecules must collide with enough energy to react d The use of a catalyst Temperature and Rate a Chemical reaction rates GENERALLY increase with temperature not always though b The Collision Model i e collision theory i Reaction rates depend on collisions which in turn will likely depend on at least 3 factors ii Collision frequency the number of collisions per second per liter 1 Higher concentration and higher temperature more frequent collisions iii Collision energy the fraction of the collisions that are sufficiently forceful 1 Powerful collision reaction 2 Gentle collision no reaction iv Collision orientation the fraction of the collisions with correctly oriented molecules 1 Correct alignment reaction c Activation Energy the minimum collision energy required for molecules to react i Activate complex transition state ii Typically only a fraction of the molecules in a sample possess sufficient energy to react iii Higher the temperature the higher this fraction d The Arrhenius Equation i If the reaction rate varies with temperature so must the rate constant ii k Ae E RT 1 E activation energy 2 A frequency factor 3 R gas constant 8 314 J mol K 4 Temperature in kelvin 5 Higher T larger K increased rate
View Full Document
Unlocking...