Rates Of Reaction
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Increasing Temperature
Increases KE More collisions per unit volume More successful collisions per unit time Rate of Reaction increases
Increasing Concentration
More particles per unit volume Collision frequency is higher More successful collisions per unit time Rate of reaction increases
Increase Surface area
more solid is exposed to other particles Collision frequency is higher More successful collisions per unit time Rate of reaction increases
What does a catalyst do?
A catalyst provides an alternative route with a lower activation energy
Add a catalyst
Frequency of collisions with enough energy is higher More successful collisions per unit time Rate of Reaction increases
Practical: Reacting Sodium thiosulphate with Hydrochloric acid Aim: To determine the effect of concentration on rate of reaction
Independent variable - concentration of sodium thiosulphate Dependent variable - Time take for cross to disappear Control variables - temperature, concentration of HCl, volume of the solution Observations - solid sulphur is produced, black cross gradually disappears
How is rate calculated?
Rate = 1/ time taken
Practical: Reacting calcium carbonate chips with Hydrochloric acid Aim: To determine the effect of surface area on the rate of reaction
Independent variable - size of calcium carbonate chips Dependent variable - volume of CO2 produced Control variables - mass of calcium carbonate, volume and concentration os HCl, temperature Observations - calcium carbonate chips dissolve in Hydrochloric acid Equation: CaCO3 + 2HCl —> CaCl2 + H2O + CO2
Practical: Reacting Magnesium with Hydrochloric acid Aim: to determine the effect of temperature on the rate of reaction
Independent Variable: Temperature of HCl Dependent Variable: time taken for Mg (s) to disappear Control Variable: Mass and SA of Mg, volume and concentration of HCL Observations: Magnesium solid dissolves
What do catalysts do?
Increase rate of reaction Remain chemically unchanged
Practical: Decomposition of Hydrogen Peroxide Aim: to determine the effect of ac catalyst on the rate of reaction Catalyst is magnesium oxide - black solid Catalyst are not included in equation because they are unchanged during the reaction
Independent variable: Catalyst being used Dependent Variable: Volume of Oxygen produces Control Variable: Volume and Concentration of Hydrogen peroxide, temperature, mass and surface area of catalyst Equation: 2H2O2 —> 2H2O + O2