Rates of Reaction Flashcards
rate of reaction =
amount of reactant used up / time taken
what is activation energy
the minimum amount of energy needed by the reactant particles to react on collision
what is an endothermic reaction
heat energy is taken in from the surroundings
what is an exothermic reaction
heat energy is given out from the surroundings
what happens to the rate of reaction as temperature increases
rate of reaction increases
why does rate of reaction increase as temperature increases
when temperature increases the particles move faster so they collide more frequently. Further, the particles collide with greater energy so more of the reactant particles have enough energy greater than activation energy to react on collision. There are more successful collisions per unit time hence the rate of reaction increases
how do you increase the temperature
warm the solution / acid
how do you increase the surface area of a solid reactant
crush the …. with a pestle and mortar
why are three experiments done and not only one
to improve the reliability of the investigation
to identify anomalous results
to be able to calculate an average value
how does concentration increase the rate of reaction
when the concentration of a solution is increased there are more reactant particles in the same volume. There is a greater chance of the reactant particles colliding, so the frequency of collisions increases and the rate of reaction increases
if hydrogen was being produced, why can the rate of reaction not be measured by measuring the mass of the reactants with time
Hydrogen has a very low molar mass, so the change in mass would be too small to measure
what are the 3 ways the volume of gas produced in a reaction can be measured accurately
use a gas syringe
collect the gas over water using an inverted measuring cylinder of water
collect the gas over water using an inverted burette of water
new concentration =
volume of acid / total volume x original concentration of acid
how can the student control the volume of acid used in each experiment
water can be added to make all the total volumes the same
what are the possible causes for an anomalous result for the volume of gas
there was an error in measuring the volume of gas
the conc of acid was incorrect
there was a change in temp
some has escaped from the flask
there was a timing error
there was a plotting error
why does pressure increase the rate of reaction
when a pressure is increased the particles are pushed closer together so there are the same number of particles but in a smaller volume. There are more reactant particles per unit volume so the frequency of collisions increases and rate of reaction increases
how does surface area increase the rate of reaction
the powder has a larger surface area than the solid so more particles are exposed to the acid particles. There is a greater surface for collisions to take place with the acid particles. The frequency of collisions increases and the rate of reaction increases
how does a catalyst speed up the rate of reaction
a catalyst provides an alternative reaction route that requires a lower activation energy. This speeds up the reactions because more of the reactant particles have enough energy, greater than activation energy, to react on collision, so more successful collisions occur.
why are catalysts useful in industry
they reduce energy costs
what happens to catalysts at the end of a reaction
it remains chemically unchanged and its mass stays the same at the end of the reaction
