Rate and extent of chemical change Flashcards
mean rate of reaction equation
mean rate of reaction =
quantity of reactant used /
time taken OR quantity of product formed / time taken
How does the concentrations of reactants in solution and pressure affect the rate of reaction?
If a solution is more concentrated, there are more particles colliding in the same volume of water. Similarly, when the pressure of a gas is increased, it means that the same number of particles occupies a smaller space. This makes collisions between the reactant particles occupies a smaller space. This makes collisions between the reactant particles more frequent.
How does increasing the temperature affect the rate of reaction?
When the temperature is increased, the particles move faster as they gain kinetic energy. Since they are moving faster, they collide more frequently. Since they have more energy they will typically have enough energy for successful collisions also for the reaction to take place.
How does increasing the surface area affect the rate of reaction?
Breaking up a solid into smaller pieces will increase its surface area to volume ratio. For the same volume of solid, the particles around it will have more area to work on - so there will be collisions more frequently.
How does the presence of a catalyst affect the rate of reaction?
A catalyst is a substance that speeds up a chemical reaction without being used up in the reaction itself. This means it’s not part of the overall reaction equation. Catalysts work by providing an alternate reaction pathway with a lower activation energy.
What is collision 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.
Why does increasing the concentration of reactants in solution, the pressure of reacting gases, and the surface area of solid reactants increase the rate of reaction?
Because it increases the frequency of collisions.
Why does increasing the temperature increase the rate
of reaction?
Because it increases the frequency of collisions
and makes the collisions more energetic.
When do enzymes act as catalysts?
In biological systems.
What are reversible reactants?
The products of the reaction can react to produce the original reactants.
If a reversible reaction is exothermic in one direction…
… It is endothermic in the opposite direction.
When is equilibrium reached?
Equilibrium is reached when the
forward and reverse reactions occur at exactly the same rate.
What does the relative amounts of all the reactants and products at equilibrium depend on?
The conditions of the reaction.
What is Le Chatelier’s principle?
If a system is at equilibrium and a change is made to any of the conditions, then the system responds to counteract the change.The effects of changing conditions on a system at equilibrium can be predicted using Le Chatelier’s Principle.
What is the effect of changing concentration?
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.
