How do chemists control the rate of reactions? Flashcards
What is rate of reaction?
a measure of how quickly a reactant is used up, or a product is formed
What is rate of reaction affected by?
concentration, pressure, temperature, and surface area to volume ratio of a solid
reactant
Why is collision theory helpful?
it helps to explain why different factors affect the rate of reaction
What is collision theory?
for a chemical reaction to happen, reactant particles must collide with each other
the particles must have enough energy for them to react
a collision that produces a reaction is a successful collision
the greater the rate of successful collisions, the greater the rate of reaction.
What happens at lower temperatures?
the particles move slowly as they have less kinetic energy
this means that the particles collide less often, and with lower energy - so
fewer collisions will be successful - rate of reaction will be slow
What happens at high temperatures?
the particles move faster as they have more kinetic energy
this means that particles collide more often, and with higher energy,
giving a faster rate of reaction.
What happens in a reaction where one or both reactants are in low concentrations?
the particles will spread out in solution and collide with each other less often, so there will
be fewer successful collisions.
What happens if there is a high concentration of one or both reactants?
the particles wll be crowded close together and collide with each other more often, so there will be more successful collisions.
What happens when a gas is under low pressure?
the particles with spread out and collide with each other less often, so there will be
fewer successful collisions
What happens when the gas is under high pressure?
the particles are crowded more closely together, and collide more often, so there will be more successful collisions
What happens when the surface area of a solid reactant is larger?
the reaction will be faster
powdered solids have a large surface area compared to volume - they have a high
surface area to volume ratio so more particles are exposed on the surface for other reactants to collide with.
the greater the number of particles exposed, the greater chance of them colliding successfully, which increases the rate of the reaction
What is a catalyst?
speeds up the rate of a reaction without being used up or changed in the reaction.
