Chapter 6 - Chemical Reactions
Collision Theory
1) For a chemical reaction to occur reactant particles need to collide with one another.
2) For products to be formed, the collision needs to have a certain minimum amount of energy associated with it, and not every collision results in the formation of products.
3) The minimum amount of energy is known as the activation energy.
4) Collisions that result in the formation of products are known as successful collisions.
Rate of reaction - Surface area
- More particles are exposed to the other reactant
- The rate of a chemical reaction can be raised by increasing the surface area of a solid reactant.
Rate of reaction - Adding or removing catalysts
- Catalyst increases the rate of a chemical reaction by providing an alternative reaction path which has a lower activation energy.
- Does not increase the number of collisions
- Causes more of the collisions to become SUCCESSFUL collisions
Definition of catalyst
A catalyst increases the rate of a reaction and is unchanged at the end of a reaction.
Rate of reaction - Concentration
- Products of a reaction are formed as a result of collisions between reacting particles
- Increasing concentration means more frequent collisions between reactant particles.
- More often particles collide, the greater chance they have of overcoming the activation energy
- More likely that a successful collision occurs.
- Rate of chemical reaction is increased due to more particles per unit volume
Rate of reaction - Pressure of gases
- An increase in the pressure increases the rate of reaction
- Gas particles are pushed closer together, increasing the number of particles per unit volume
- Particles collide more frequently, rate of reaction is increased
Rate of reaction - Temperature
- As temperature increases, reactant particles increase their kinetic energy
- Some of these particles will have greater energy than the activation energy
- More frequent collisions between faster-moving particles
- Some of the extra collisions will be successful collisions so the reaction rate to increase.
Equilibrium Definition
1) Rate of forward reaction is equal to the rate of the reverse reaction
2) Concentration of reactants and products are no longer changing.
Effect of Temperature, Pressure, Concentration, Catalyst on position of equilibrium.
1) Temperature increase, shifts equilibrium to endothermic side.
2) Pressure increase, shifts equilibrium to side with fewer moles of gas.
3) Concentration, equilibrium will shift towards the reactant when the concentration of product increases and vice versa.
4) Catalyst, does not affect position of equilibrium, but it helps reach equilibrium more quickly.
Haber process
Equation: N2(g) + 3H2(g) ->(reversible)<- 2NH3(g)
Hydrogen comes from methane and steam reaction
Nitrogen comes from air
Conditions: 450 degrees, 200 atm, iron catalyst
Contact process
Sulfur Dioxide converted to sulfur trioxide: 2SO2(g) + O2(g) ->(reversible)<- 2SO3(g)
Sulfur Dioxide found from roasting sulfide ores in air (oxygen)
Conditions: 450 degrees, 2atm, vanadium(V) oxide catalyst.