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Chem 102 Exam 2 Review

# Chem 102 Exam 2 Review - Chem 102 Exam 2 Review Rate Laws A...

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Chem 102 Exam 2 Review Rate Laws A rate law shows the relationship between the reaction rate and the concentrations of the reactants The exponents tell the order of the reaction with respect to each reactant The overall reaction order can be found by adding the exponents on the reactants in the rate law Generally, as the temperature increases, so does the reaction rate This is because k (rate constant) is temperature dependent Arrhenius Equation Arrhenius developed a mathematical relationship between R and E a K = Ae -Ea/RT where A is the frequency factor, a number that represents the likelihood that collisions would occur with the proper orientation for reaction. (Temperature doesn’t affect the activation energy (E a )) Taking the natural logarithm of both sides, the equation becomes lnk=-Ea (1/RT) + lnA y = mx + b Therefore, if k is determined experimentally at several temperatures, Ea can be calculated from the slope of a plot of lnk vs. 1/T Reaction Mechanisms The molecularity of a process tells how many molecules are involved in the process In a multistep process, one of the steps will be slower than all others The overall reaction cannot occur faster than this slowest, rate-determining step Concept of Equilibrium Chemical equilibrium occurs when a reaction and its reverse reaction proceed at the same rate As a system approaches equilibrium, both the forward and reverse reactions are occurring Once equilibrium is achieved, the amount of each reactant and product remains constant Properties of Equilibrium Equilibrium systems are

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Dynamic (in constant motion) Reversible Can be approached from either direction Depicting Equilibrium In a system at equilibrium, both the forward and reverse reactions are being carried out; as a result, we write its equation with a double arrow Rate Constants K is large for high reaction rates and is dependent on temperature Units of k vary with reaction order Rate = k [A] n [B] m aA + bB→ cC + dD Reaction orders, n and m, may be independent of stoichiometric coefficients, a and b Overall reaction order is n+m Temperature and Rate Generally, as the temperature increases, so does the reaction rate This is because k is temperature dependent Half-Life Half-life is defined as the time required for one-half of a reactant to react Note: For a 1 st order process, the half-life does NOT depend on the initial concentration Reaction Mechanisms The sequence of events that describes the actual process by which reactants become
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Chem 102 Exam 2 Review - Chem 102 Exam 2 Review Rate Laws A...

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