16.1 FACTORS THAT EFFECT REACTION
RATES
13 December 2021
18:40
Rate of reaction - Change in the amount of reactants or products per unit time.
Factors which affect the reaction rates are:
Concentration
SA of solids
Temperature
Catalysts
A catalyst increases the rate of a chemical reaction by providing an alternative
reaction route, lowering the activation energy.
Doesn't get used up and so can be recovered at the end of the reaction.
Heterogeneous catalyst - In a different phase from the reactants.
The reaction happens on the surface of the catalyst, and so increasing the SA
increases the rate of reaction.
Reactant molecules bond to the surface of the solid catalyst.
Adsorption
Bonds within the reactant molecules are weakened.
Forms radicals which react to form product molecules.
The product molecules detach from the catalyst.
Desorption
Catalytic poising is when chemicals bond irreversibly to the surface of the catalyst.
Can be regenerated by blowing hot air over the catalyst, oxidising the
chemicals.
Catalysts can reduce production costs, and can make more product in a shorter time.
Not as high temperatures needed.
Not as high pressures needed.
Catalysts can also change the properties of the product to make them more useful.
, 16.2 MEASURING REACTION RATES
13 December 2021
19:08
Gas volume:
Collect in a gas syringe and record volume of gas at regular time intervals.
Loss of mass:
If a gas is formed, the system will lose mass.
Measure mass at regular time intervals to measure mass of gas released.
Colour change:
A colourimeter will be used to measure absorbance of colour.
Plot a calibration curve of known concentrations.
Take samples at regular time intervals and record the absorbance.
Use calibration curve to find concentration of the samples taken at different
times.
Change in pH:
If reaction produce or forms H+ ions, the pH of the solution will change.
Measure pH at regular intervals to calculate concentration of H+ ions.
Titration:
Take samples at regular time intervals and quench the sample.
Titrate the samples using a standard solution.
Calculate the concentrations at each time interval.
Rate can be calculated by measuring the change in concentration over time.
Electrical conductivity:
If the number of ions change, the electrical conductivity will change.
RATES
13 December 2021
18:40
Rate of reaction - Change in the amount of reactants or products per unit time.
Factors which affect the reaction rates are:
Concentration
SA of solids
Temperature
Catalysts
A catalyst increases the rate of a chemical reaction by providing an alternative
reaction route, lowering the activation energy.
Doesn't get used up and so can be recovered at the end of the reaction.
Heterogeneous catalyst - In a different phase from the reactants.
The reaction happens on the surface of the catalyst, and so increasing the SA
increases the rate of reaction.
Reactant molecules bond to the surface of the solid catalyst.
Adsorption
Bonds within the reactant molecules are weakened.
Forms radicals which react to form product molecules.
The product molecules detach from the catalyst.
Desorption
Catalytic poising is when chemicals bond irreversibly to the surface of the catalyst.
Can be regenerated by blowing hot air over the catalyst, oxidising the
chemicals.
Catalysts can reduce production costs, and can make more product in a shorter time.
Not as high temperatures needed.
Not as high pressures needed.
Catalysts can also change the properties of the product to make them more useful.
, 16.2 MEASURING REACTION RATES
13 December 2021
19:08
Gas volume:
Collect in a gas syringe and record volume of gas at regular time intervals.
Loss of mass:
If a gas is formed, the system will lose mass.
Measure mass at regular time intervals to measure mass of gas released.
Colour change:
A colourimeter will be used to measure absorbance of colour.
Plot a calibration curve of known concentrations.
Take samples at regular time intervals and record the absorbance.
Use calibration curve to find concentration of the samples taken at different
times.
Change in pH:
If reaction produce or forms H+ ions, the pH of the solution will change.
Measure pH at regular intervals to calculate concentration of H+ ions.
Titration:
Take samples at regular time intervals and quench the sample.
Titrate the samples using a standard solution.
Calculate the concentrations at each time interval.
Rate can be calculated by measuring the change in concentration over time.
Electrical conductivity:
If the number of ions change, the electrical conductivity will change.
