3(b) Rates of Reaction Flashcards
Factors that affect the rate of reaction
- Surface Area
- Concentration (for liquids), Pressure (for gases)
- Temperature
- Catalyst
Effect of Surface Area on Rate of Reaction
smaller particles = higher total surface area
so greater frequency of successful collisions
Effect of Concentration/Pressure on Rate of Reaction
Higher concentration = particles closer together + more particles in the same volume
so greater frequency of successful collisions
Effect of Temperature on Rate of Reaction
higher temperature increeases K.E. so particles move faster + more particles meet activation energy requirements
so greater frequency of successful collisions
Catalyst
increases the rate of reaction
remains chemically unchanged
Lowers activation energy
Provides an alternative pathway for the reaction to occur
Examples of Exothermic Reactions
- Combustion
- Oxidation
- Neutralisation
Examples of Endothermic Reactions
Decomposition
Marble Chips Experiment
Put marble chips in conical flask and measure HCl in measuring cylinder.
Put everything on an electric balance and set to zero.
Add HCl to conical flask and put cotton wool on (allows gas to escape without acid spitting out)
Record reading on balance every 30 seconds
Marble Chips Experiment: Investigate S.A and Conc. of acid
S.A. - repeat experiment with different sized marble chips
Conc. of acid - repeat experiment with different conc. HCl
Practical: investigate the effect of different solids on the catalytic decomposition of hydrogen peroxide solution
Put hydrogen peroxide solution and manganese oxide powder in conical flask and connect to gas syringe
Check reading (for O2) every 20 seconds
Repeat experiment with lead oxide, copper oxide
Halving conc. halves rate of reaction
Practical: Dissappearing Cross
Sodium Thiosulfate + HCl -> Hydrogen + Sodium Chloride + Water
Draw cross on some paper and put under conical flask (containing sodium thiosulfate)
Add acid and start timer
Stop timer when cross dissapears
Repeat and work out average
