Physical Chemistry - Rates of Reaction

rate of reaction = amount of reactant used or product created/time

• marble chips react with hydrochloric acid (HCl) to produce carbon dioxide gas and calcium chloride solution • add marble chips to hydrochloric acid in a beaker with cotton wool on the top (so carbon dioxide can escape but no acid can) • measure with a balance • measure the mass of carbon dioxide lost at intervals • vary the surface area of the marble chips, the concentration of acid or the temperature.

• hydrogen peroxide naturally decomposes slowly producing water and oxygen gas, manganese (IV) oxide can be used as a catalyst to speed up the rate of reaction • the rate of reaction can be measured by measuring the volume of oxygen produced at regular intervals using a gas syringe

increasing the surface area of a solid increases the rate of a reaction - more particles exposed - more frequent collisions per unit time - increase the rate of a reaction

increasing the concentration of a solution increases the rate of a reaction - more particles in same space - more frequent collisions per unit time - increase rate of reaction

increasing the pressure of a gas increases the rate of a reaction

increasing the temperature increases the rate of a reaction - particles have more kinetic energy - more frequent collisions and a higher proportion of those collisions are successful because the collision energy is greater or equal to the activation energy - increase rate of reaction

using a catalyst increases the rate of a reaction

a catalyst is a substance that increases the rate of a reaction (by providing an alternate pathway with a lower activation energy) but is chemically unchanged at the end of the reaction.

• manganese dioxide • liver • potato • potassium iodide • copper oxide • sodium chloride only some of these are effective catalysts when used with hydrogen peroxide. if they arent, there will be no bubbles of oxygen produced