U1- Rates Flashcards
*activation energy
the minimum amount of energy required for a reaction to take place
rate of reaction
the change in concentration of a reactant or product per unit time
temperature
measure of the kinetic energy of the particles in a substance
catalyst
a substance which speeds up a chemical reaction by lowering the activation energy, remaining unchanged by the reaction
Maxwell-Boltzmann Distribution Curve
a graph showing the distribution of energy across a sample of particles
average rate of reaction
the change in concentration of a reactant or product per unit time as measured over a certain time period. (change in quantity)/(change in time)
reversible reaction
a chemical reaction that can occur in either the forward or reverse direction, given appropriate conditions
closed system
a system in which no substances can be escape or be added
dynamic equilibrium
a situation in which the rate of the forward and reverse reactions are equal resulting in no observable changes over time
yield
the amount of product produced
position of equilibrium
an evaluation of the relative amount of products compared to reactants, at equilibrium.
on the right if more products are present
on the left if more reactants are present
Le Chatelier’s Principle
a system at equilibrium has a tendency to partially oppose a disruption
collision theory
for a successful collision to occur, reactant particles must collide with the correct orientation and sufficient energy (= or > Ea)
factors affecting rates of reaction
surface area (solids) temperature concentration pressure (gas) catalyst
Boyle’s Law
a decrease in volume will increase the pressure
an increase in volume will decrease the pressure
how does the use of catalysts affect the rate of reaction
catalysts lower the activation energy of reactants, increasing the proportion of particles with energy equal to or greater than the activation energy. This increases the frequency of successful collisions therefore increasing rate of reaction.
overall reaction is unchanged hw chemical pathway is altered.
homogeneous vs heterogenous catalyst
homogeneous= same state as reactants heterogenous= different state to reactants
how does an increase in surface area affect rate of reaction
(SA is increased)
more particles are exposed to the other reactant(s) and the collision frequency increases.
There is a greater frequency of successful collisions between particles
The rate of reaction increases
how does an increase in temperature affect the rate of reaction
the average kinetic energy increases
resulting in a greater proportion of particles having energy equal to or greater than the activation energy
resulting in a higher proportion of successful collisions, and thus a higher frequency of successful collisions
therefore rate of reaction increases
how does an increase in concentration/pressure affect the rate of reaction
[as volume decreases (pressure)] there is a higher number of reactant particles per unit volume
increasing the collision frequency
there is a greater frequency of successful collisions between particles
the rate of reaction increases
activated complex
unstable arrangement of atoms bw reactants and arrangement of products
positive delta H
endothermic reaction
negative delta H
exothermic reaction
enthalpy
chemical energy
haber process
N2 + 3H2 < - > 2NH3
400-450 degrees
200atm
Iron catalyst
