Rates Of Reaction

A substance that increases the rate of reaction but is chemically unchanged at the end of the reaction

By providing an alternative pathway with lower activation energy

-increases the rate of reaction -particles gain more kinetic energy so move faster -they therefore collide more frequently increasing the rate of reaction -increase in the number of particles with energy greater than or equal to the activation energy -so more successful collisions, increasing rate of reaction

-decreases the rate of reaction -decreases the number of particles within a fixed volume -therefore particles are further apart so collide less frequently -fewer frequent successful collisions so rate of reaction decreases

-increases the rate of reaction -particles are forced closer together as they are in a smaller volume -particles collie more frequently -more frequent successful collisions so rate of reaction increases

-decreases the rate of reaction -less particles on the surface are exposed and able to collide and react -particles collide less frequently -less frequent successful collisions

• Measure a volume of hydrogen peroxide (10cm^3) into four separate boiling tubes • Add your first catalyst e.g copper (II) oxide to one of the boiling tubes and record observation • At the end of the experiment, weigh a piece of filter paper and then filter the mixture retaining the residue. Rinse the boiling tube will distilled water and pour the rinsings into the filter paper to collect all of the remaining solid. • Allows the filter paper to dry and then e-weigh the filter paper and residue • Repeat with different catalysts • This experiment can also be used to measure the volume of gas produced. Repeats steps 1 and 2 and then measure the oxygen produced using a gas syringe. However error can be created if gas escapes when the bung is put on.

2H2O2 (aq) —> 2H2O(l)+O2(g)

-the mass recorded may be lower than expected as not all the solid was transferred -the mass may be higher than expected as the solid was not completely dry

• wear eye protection and Take care when using hydrogen peroxide as it is corrosive and a irritant

-manganese (IV) oxide is the most effective catalyst as it speeds up reaction and remains chemically unchanged (same mass) -copper (II) oxide is a weak catalyst -although potassium iodide speeds up reaction it loses mass so not a catalyst

• Use a measuring cylinder to measure 25cm^3 of dilute hydrochloric acid • Add 5g of large marble chips to a conical flask and place a piece of cotton wool at the opening of the flask. The cotton wool allows the carbon dioxide to escape during the reaction but prevents acid spray from leaving the flask. The marble is in excess so some of it will be left over when all the acid is used up • Place everything on a balance and reset it to zero • Add the acid to the marble chips and record the readings on the balance every 30 seconds

-the mass goes down as the carbon dioxide escapes through the cotton wool

-cannot be used for soluble gases as they cannot escape the solution

-repeats experiment on rate of reaction but use smaller marble chips which increases the surface area -therefore the rate of reaction is faster but the same mass of carbon dioxide is produced but in this experiment is quicker -this is because the surface area in contact with the gas or liquid is much greater and there are more particles of solid exposed on the surface. Only particles on the surface are available for collisions. Therefore as the surface area of the solid increases, there are more frequent successful collisions

-repeat same rates of reaction experiment but use different concentrations of acid and keep everything else the same -increasing the concentration, increases the rate of the reaction