10.1 Reaction Rates Flashcards
What does rate of reaction measure?
How fast a reactant is being used up or how fast a product is being formed
What is rate of reaction?
Change in concentration of a reactant or a product in a given time
Rate equation and units
Change in concentration/time
Units - moldm^-3s^-1
When is rate of reaction at its highest?
At the start of the reaction, as each reactant is at its highest concentration
Why does rate of reaction decrease as reaction proceeds?
Reactants are being used up and concentrations decrease
Factors affecting rate of reaction
Concentration (aq) Pressure (g) Temperature Use of catalyst Surface area (s)
Collision theory
2 reacting particles must collide for a reaction to occur
When will a collision be effective?
Particles collide with the correct orientation
Particles have sufficient energy to overcome activation energy barrier of the reaction
Temperature and rate of reaction
Increasing temperature = increasing rate of reaction
Particles have greater kinetic energy, move around more
Greater frequency of collisions, greater frequency of successful collisions
Also, greater proportion of particles have activation energy
Concentration and rate of reaction (or pressure in gases)
Increasing concentration = increasing rate of reaction
Particles become more crowded
Greater frequency of collisions, more successful collisions
Catalysts and rate of reactions
Catalysts increase the rate of reaction
Provide alternative reaction pathway with lower activation energy
Greater proportion of particles have activation energy
Rate of successful collisions increases compared to rate in an uncatalysed reaction
Surface area and rate of reaction
More surface area = increased rate of reaction
More reactant particles are available for collisions
Collisions are more likely so particles collide more often
How can progress of a reaction be measured?
Monitor removal of a reactant
Measure formation of product
Methods for measuring gas produced
Monitoring gas produced using a gas syringe - check at regular intervals
Using an upturned measuring cylinder in water
How can rate of reaction be measured?
Monitor volume of gas produced at regular time intervals
Monitor loss of mass of reactants using a balance
