Contents
A rate law is an equation that relates the rate of a chemical reaction to the concentrations of the reactants. The rate law can be used to predict the rate of the reaction at any given point.
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Introduction
A rate law is an equation that describes how the rate of a chemical reaction changes with respect to the concentration of reactants. The rate of a reaction is the speed at which reactants are converted into products. The most common form of a rate law is:
Rate = k[reactant1]^a[reactant2]^b
In this equation, k is the rate constant and is a measure of how fast the reaction will proceed. The exponents (a and b) are the reaction orders and are a measure of how the reactant concentrations affect the reaction rate. The overall reaction order is determined by adding the powers to which each reactant concentration is raised in the rate law equation.
What is a rate law?
In chemistry, a rate law is an equation that relates the rate of a chemical reaction to the concentrations of reactants and products. The rate law can be used to predict how a reaction will proceed at different concentrations of reactants. It can also be used to determine the order of a reaction and the rate constant for that reaction.
The rate law equation
The rate law equation is a mathematical expression that relates the reaction rate to the concentrations of the reactants. The rate law equation is used to determine the kinetics of a reaction, which is the study of how reactions occur. The rate law equation can be used to determine the rate constant, which is a measure of how fast a reaction occurs. The rate law equation can also be used to determine the order of a reaction, which is a measure of how the concentrations of the reactants affect the reaction rate.
Units of the rate law
The units of the rate law tell us about the dimensions (units) of the concentration term in the rate law. The rate law for a reaction
A + B --> products
is
rate = k[A]^x[B]^y
The units of k are
-M^(-x-y)L^(x+y)T^(-1)
if we assume that molar concentrations are used for [A] and [B].
How to determine the rate law?
In order to determine the rate law for a chemical reaction, you need to know the following:
1) The overall reaction order (the sum of the orders of all reactants)
2) The individual orders of each reactant
3) The rate constant for the reaction
The easiest way to determine the overall reaction order is to run a series of experiments at different concentrations and then fit a line to the data. The slope of this line will be equal to the overall reaction order.
To determine the individual orders of each reactant, you need to run experiments at different concentrations of each reactant while holding the concentrations of all other reactants constant. For each reactant, you will fit a line to the data and the slope of this line will be equal to the order of that particular reactant.
Once you know the overall reaction order and the individual orders of each reactant, you can determine the rate law for the reaction. The rate law is simply an equation that relates the reaction rate to the concentrations of reactants.
The importance of the rate law
The rate law for a particular reaction is a very important piece of information. It allows us to predict how the rate of the reaction will change as the concentrations of the reactants are changed. For example, if we know that the rate law for a reaction is first order in A, we can predict that doubling the concentration of A will double the rate of the reaction.
Rate laws also allow us to determine the overall order of a reaction. The overall order of a reaction is simply the sum of all of the exponents in the rate law equation. In our example above, the overall order would be 1 + 0 = 1. In general, we expect reactions that have a higher overall order to occur more quickly than reactions with a lower overall order.
Finally, the rate law can give us information about the mechanism of a reaction. If we know that a particular reaction is second-order in A and zero-order in B, we can conclude that A must be reacting with itself (since it is second-order) and that B is not involved in the rate-determining step (since it is zero-order).
The factors that affect the rate law
In a chemical reaction, the rate law (or rate equation) is an equation that relates the rate of the reaction to the concentrations of reactants. The form of the rate law is determined experimentally and is independent of any theory. The order of a reaction with respect to a given reactant is the sum of the stoichiometric coefficients of that reactant in the overall balanced chemical equation for the reaction. The overall or apparent order of a reaction is determined by experiment and is given by the exponent in the rate law expression.
The rate law and the reaction mechanism
In a chemical reaction, the rate law is a mathematical expression used to predict how the rate of the reaction will change with changes in the concentrations of reactants. The rate law is derived from the kinetic model of a chemical reaction, which takes into account the number and kind of particles taking part in the reaction, as well as the energies of their collisions. In general, the rate law for a reaction can be written as follows:
rate = k[A]^m[B]^n
where k is the rate constant, [A] and [B] are the concentrations of reactants A and B, and m and n are the orders of reaction with respect to reactant A and B. The order of a reaction is determined by observing how the rate of the reaction changes as the concentration of a reactant is changed. For example, if doubling the concentration of reactant A results in a doubling of the rate of reaction, then the order of reaction with respect to reactant A is 1. If doubling the concentration of reactant A results in quadrupling of the rate, then the order with respect to reactant A is 2. Zero order reactions have rates that are independent of concentration (i.e. adding more reagent does not change how quickly product forms).
The mechanism isthe “step-by-step” details explaining how exactly a chemical reaction occurs. It includes an explanation for how each step leads into another until finally products are formed.
+Important things to include: Arrhenius equation, catalyst
The rate law and the order of the reaction
The rate law for a reaction gives the mathematical relationship between the rate of the reaction and the concentrations of the reactants. The rate law can be used to determine the order of the reaction, which is the power to which the concentration of each reactant is raised in the rate law equation. The order of a reaction can be zero, first, second, or higher.
Summary
In a chemical reaction, the rate law is a mathematical expression that relates the rate of the reaction to the concentrations of the reactants. The rate law can be used to predict the rate of the reaction at any given point in time, provided that the concentrations of the reactants are known. In most cases, the rate law is determined experimentally by measuring the rates of reaction at different concentrations of reactants.
The rate law for a particular reaction is typically expressed as follows:
rate = k[A]^a[B]^b…
where k is the rate constant for the reaction, [A], [B], etc. are the concentrations of reactants A, B, etc., and a, b, etc. are their respective stoichiometric coefficients (the number of molecules of each reactant that are involved in a single molecule of product).
