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# Chemical Kinetics ## Reaction Rate ### Definition The reaction rate is the change in concentration of reactants or products per unit time. ### Rate Law The rate law expresses the relationship between the rate of a reaction and the concentration of the reactants. For a reaction: $aA + bB \ri...

# Chemical Kinetics ## Reaction Rate ### Definition The reaction rate is the change in concentration of reactants or products per unit time. ### Rate Law The rate law expresses the relationship between the rate of a reaction and the concentration of the reactants. For a reaction: $aA + bB \rightarrow cC + dD$ The rate law is: $rate = k[A]^m[B]^n$ Where: * $k$ is the rate constant * $[A]$ and $[B]$ are the concentrations of reactants * $m$ and $n$ are the orders of reaction with respect to A and B, respectively. ### Order of Reaction The overall order of a reaction is the sum of the individual orders with respect to each reactant. $overall\,order = m + n$ ### Rate Constant The rate constant ($k$) is a temperature-dependent constant that reflects the speed of the reaction. ## Factors Affecting Reaction Rate ### Temperature Increasing temperature generally increases the reaction rate. ### Concentration Increasing the concentration of reactants generally increases the reaction rate. ### Catalyst A catalyst speeds up a reaction without being consumed in the process. ### Surface Area For heterogeneous reactions, increasing the surface area of solid reactants increases the reaction rate. ## Activation Energy ### Definition Activation energy ($E_a$) is the minimum energy required for a reaction to occur. ### Arrhenius Equation The Arrhenius equation relates the rate constant ($k$) to the activation energy ($E_a$) and temperature ($T$). $k = Ae^{-\frac{E_a}{RT}}$ Where: * $A$ is the pre-exponential factor * $R$ is the gas constant ($8.314 J/mol \cdot K$) * $T$ is the temperature in Kelvin ## Reaction Mechanisms ### Elementary Steps A reaction mechanism is a series of elementary steps that describe the overall reaction. ### Rate-Determining Step The rate-determining step is the slowest step in the reaction mechanism, which determines the overall rate of the reaction. ## Catalysis ### Homogeneous Catalysis The catalyst is in the same phase as the reactants. ### Heterogeneous Catalysis The catalyst is in a different phase from the reactants. ## Summary Table | Term | Definition | | ------------------- | ------------------------------------------------------------------------------ | | Reaction Rate | Change in concentration of reactants or products per unit time | | Rate Law | Expression relating reaction rate to reactant concentrations | | Order of Reaction | Sum of the exponents in the rate law | | Rate Constant | Temperature-dependent constant reflecting reaction speed | | Activation Energy | Minimum energy required for a reaction to occur | | Reaction Mechanism | Series of elementary steps describing the overall reaction | | Rate-Determining Step | Slowest step in the reaction mechanism, determining the overall reaction rate | | Catalyst | Substance that speeds up a reaction without being consumed |