rate & extent of chemical change Flashcards
what is collision theory?
the theory that chemical reactions can only occur when reacting particles collide with each other with sufficient energy
what is activation energy?
minimum amount of energy that particles must have to react
describe the effect of increasing temperature on rate of reaction
- particles have more energy
- more collisions have energy higher than activation energy
- higher frequency of collisions
describe the effect of increasing concentration on rate of reaction
- more particles in the same volume
- particles closer together
- higher frequency of collisions
describe the effect of increasing pressure on rate of reaction
- particles closer together
- higher frequency of collisions
describe the effect of increasing surface area on rate of reaction
- more surface available for collisions
- higher frequency of collisions
how do catalysts work?
increase rate of reaction without being used up, by providing an alternative reaction pathway with a lower activation energy
why are catalysts are used in industry?
- reduces temperature required for a reaction - lowers energy costs
- catalysts can be reused
- reactions are quicker
define a reversible reaction
where products of reaction can react to produce original reactants
how can the direction of a reversible reaction be changed?
by changing the conditions of the reaction
if a reversible reaction is exothermic in one direction, what kind of reaction will it be in the other direction?
endothermic in the opposite direction, and the same amount of energy is transferred in each case
when is equilibrium achieved?
when a reversible reaction occurs in apparatus which prevents escape of reactants and products and the forwards and reverse reactions occur at exactly the same rate
what do the relative amounts of all reactants and products at equilibrium depend on?
the conditions of the reaction
what is Le Chatelier’s Principle used for?
used to make predictions about reactions at equilibrium
What is Le Chatelier’s principle?
if a system at equilibrium and a change is made to any conditions, the system will respond to counteract the change
what are the factors affecting a reaction at equilibrium?
- concentration of reactants or products
- pressure - if reaction involves gases
- temperature
- catalysts
if concentration of a reactant is increased, what will happen to equilibrium?
more products will be formed until equilibrium is reached again (forward reaction favoured)
if concentration of a product is increased, what will happen to equilibrium?
less products will be formed until equilibrium is reached again (reverse reaction favoured)
in an equilibrium reaction, an increase in pressure causes the equilibrium position to shift towards which side?
the side with the smaller number of molecules
in an equilibrium reaction, a decrease in pressure causes the equilibrium position to shift towards which side?
the side with the larger number of molecules
in an equilibrium reaction, an increase in temperature will favour which reaction?
the endothermic
in an equilibrium reaction, an decrease in temperature will favour which reaction?
the exothermic
