Kinetics
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Rate of reaction
the speed at which reactants are used up or products are formed, or the change in concentration of reactants or products per unit time
instantaneous rate of reaction
the rate of a reaction at a specific time period when the concentrations of reactants and products change by a negligible amount
initial rate of reaction
the speed at which reactants are used at the start of a reaction
tangent line
the line through a pair of infinitely close points on the curve, used to find the instantaneous rate of reaction
gradient
the derivative of the curve at that point, used to find the instantaneous rate of reaction. (slope of the tangent line)
kinetic molecular theory
• Gases are composed of a large number of particles that behave like hard, spherical objects in a state of constant, random motion. • These particles move in a straight line until they collide with another particle or the walls of the container. • These particles are much smaller than the distance between particles. Most of the volume of a gas is therefore empty space. • There is no force of attraction between gas particles or between the particles and the walls of the container. • Collisions between gas particles or collisions with the walls of the container are perfectly elastic. None of the energy of a gas particle is lost when it collides with another particle or with the walls of the container. • The average kinetic energy of a collection of gas particles depends on the temperature of the gas and nothing else.
kinetic energy
a property of a moving object or particle and depends not only on its motion but also on its mass.
collision theory
a method that is used to explain the variation of rate of reaction. A reaction can occur only when two particles collide in the correct orientation an with E > Ea
unsuccessful collision
a collision that does not create a new bond
successful collision
a collision that creates a new bond
activation energy
the minimum energy that colliding particles must have before collision results in a chemical reaction
energy profile
a representation of the most favourable energetic pathway for the reactants to be transformed into the products
reaction coordiante
an abstract one-dimensional coordinate chosen to represent progress along a reaction pathway.
transition state
a chemical reaction is a particular configuration along the reaction coordinate
maxwell-boltzmann energy distribution curve
describes the distribution of speeds among the particles in a sample of gas at a given temperature. The distribution is often represented graphically, with particle speed on the x-axis and relative number of particles on the y-axis
catalyst
a substance that increases the rate of a chemical reaction without itself undergoing any permanent chemical change
intermediate
a species which appears in the mechanism of a reaction, but not in the overall balanced equation. An intermediate is always formed in an early step in the mechanism and consumed in a later step.
enzymes
catalysts that speed up the rate of reactions in biological chemistry. They are made of amino acids that react with substrates to form an enzyme-substrate complex