The rate and extent of chemical change Flashcards
How can the rate of reaction be found?
The rate of a chemical reaction can be found by measuring the quantity of a reactant used or the quantity of product formed over
time
How can the quantity of a reactant or product be measured?
The quantity of reactant or product can be measured by the mass in grams or by a volume in cm3
What factors affect the rates of chemical reactions?
Factors which affect the rates of chemical reactions include: the concentrations of reactants in solution, the pressure of reacting gases, the surface area of solid reactants, the temperature and the presence of catalysts
How does the collision theory explain how various factors affect rates of reactions?
Collision theory explains how various factors affect rates of
reactions. According to this theory, chemical reactions can occur only when reacting particles collide with each other and with sufficient energy. The minimum amount of energy that particles must have to react is called the activation energy.
How does the increasing the concentration of reactants affect pressure?
Increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increases the frequency of collisions and so increases the rate of reaction.
How does increasing the temperature affect the collisions of a reaction?
Increasing the temperature increases the frequency of collisions and makes the collisions more energetic, and so increases the rate
of reaction.
What do catalysts do?
Catalysts change the rate of chemical reactions but are not used up during the reaction. Different reactions need different catalysts.
Enzymes act as catalysts in biological systems.
Catalysts increase the rate of reaction by providing a different pathway for the reaction that has a lower activation energy.
What are reversible reactions?
In some chemical reactions, the products of the reaction can react to produce the original reactants. Such reactions are called
reversible reactions
How does the direction of reversible reactions change?
The direction of reversible reactions can be changed by changing the conditions.
What is an example of a reversible reaction?
ammonium chloride
If a reversible reaction is exothermic in one direction, what will it be in the other?
If a reversible reaction is exothermic in one direction, it is endothermic in the opposite direction. The same amount of energy is transferred in each case.
How does reversible reactions in apparatus change it?
When a reversible reaction occurs in apparatus which prevents the escape of reactants and products, equilibrium is reached when the forward and reverse reactions occur at exactly the same rate.
What do the relative amounts of reactants and products at equilibrium?
The relative amounts of all the reactants and products at equilibrium depend on the conditions of the reaction.
What happens if a change is made to the conditions?
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.
What is Le Chatelier’s Principle?
If the concentration of one of the reactants or products is changed, the system is no longer at equilibrium and the concentrations of all the substances will change until equilibrium is reached again.
