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Rate of reaction ==general concept
 

Rate of reaction ==general concept

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    Rate of reaction ==general concept Rate of reaction ==general concept Presentation Transcript

    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
    • What is the rate of a reaction The rate of the reaction is how quickly the reaction happens. Fast reaction Slow reaction
    • Iron rusting - a CHEMICAL REACTION with a slow reaction rate. Wood burning - a CHEMICAL REACTION with a fast reaction rate .
    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
    • "You can’t react if you don’t collide." collision theory
        • 1. the molecules must collide to react.
      • If two molecules simply collide, however, they will not always react; therefore, the occurrence of a collision is not enough.
      3 necessary requirements in order for a reaction to take place:
    • This is the idea of a transition state ; if two slow molecules collide, they might bounce off one another because they do not contain enough energy to reach the energy of activation and overcome the transition state (the highest energy point).
        • 2. there must be enough energy (energy of activation) for the two molecules to react.
    • For the reaction to occur between two colliding molecules, they must collide in the correct orientation , and possess a certain, minimum, amount of energy .
        • 3. the molecules must be oriented with respect to each other correctly.
      • If the colliding particles have less than this minimum energy then they just bounce off each other and no reaction occurs. This minimum energy is called the activation energy.
      collision theory
      • There is a minimum amount of energy which colliding particles need in order to react
      • chemical reaction only occur between particles when they collide
    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
    • Prevent Effective collision Camera to detect fast moving traffic
    • Reactants moving too slowly Molecules bounce ( no reaction) NO 3(gas) + CO (gas)        NO 2(gas) + CO 2(gas)                                                                                                                                                                                                          NOT Effective collision
    • NO 3(gas) + CO (gas)        NO 2(gas) + CO 2(gas)                                                                                                                                                                                                          Reactants not facing right way Molecules bounce ( no reaction) NOT Effective collision
    • Reactants energy is high & oriented right way Reaction happens Effective collision
    • The orientation of collision                                                 Effective collision
    • Effective collision
    • Effective collision Which collision is effective?
    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
      • The energy that must be overcome in order for a chemical reaction to occur
      • Activation energy is the minimum energy necessary for a specific chemical reaction to occur
      • For chemical reaction to have noticeable rate, there should be noticeable number of molecules with the energy equal or greater than the activation energy.
      Activation energy
    • The sparks generated by striking steel against a flint provide the activation energy to initiate combustion in this Bunsen burner Activation energy
    • A little activation energy is added with the aid of a weed burner... What is activation energy
    • Not enough kinetic energy for reactants to leap over reaction barrier. A "hot" reaction in progress showing reactants leaping over the activation energy barrier What is activation energy
    • Activation energy
    • Activation energy
    • Only collisions with enough energy react to form products. The critical amount of energy to make the reaction proceed What is activation energy
    • A + B  C + D reactants products
    • What is activation energy activation energy
    • What is activation energy reactants products Activation energy
    • What is activation energy reactants products Activation energy
    • What is activation energy reactants products
    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
    • What affects the rate of a reaction? Size of reactant Concentration of reactants /pressure Temperature of reaction mixture catalyst
    • 1. The effect of particle size What affects the rate of a reaction?
    • 1. The effect of particle size
    • What affects the rate of a reaction? 1. The effect of particle size
      • Reducing the size of particles
      • increases the surface area
      • increases the number of collisions per second.
      • Increase the rate of reaction .
      • Increase the number of effective collisions .
    • Increasing the Surface Area of a Solid. A solid in a solution can only react when particles collide with the surface. The bigger the area of the solid surface, the more particles can collide with it per second A powder has the largest surface area and will have the fastest reaction rate.
    • THE EFFECT OF SURFACE AREA ON REACTION RATES a reaction between magnesium metal and a dilute acid like hydrochloric acid. Increasing the number of collisions per second increases the rate of reaction.
    • THE EFFECT OF SURFACE AREA ON REACTION RATES Magnesium metal
    • THE EFFECT OF SURFACE AREA ON REACTION RATES Magnesium metal
    • What affects the rate of a reaction? 2. Temperature Increasing temperature will increase energy in the particles leads to an increased probability of favourable collisions .
    • What affects the rate of a reaction? 1. The effect of temperature
      • Increase the temperature
      • increases the kinetic energy of particles
      • Increases the number of collisions per second.
      • Increase the rate of reaction .
      • Increase the number of effective collisions .
    • 3. Concentration and Pressure Increasing concentration or pressure increases the rate of a reaction, because the particles are closer together and have an increased probability of favourable collisions. What affects the rate of a reaction?
    •  
    • THE EFFECT OF CONCENTRATION ON REACTION RATES
    • THE EFFECT OF CONCENTRATION ON REACTION RATES
    • What affects the rate of a reaction? 1. The effect of concentration
      • Increase the concentration
      • increases the no of particles /unit volume
      • increases the number of collisions per second.
      • Increase the rate of reaction .
      • Increase the number of effective collisions .
    • THE EFFECT OF PRESSURE ON REACTION RATES
    • THE EFFECT OF PRESSURE ON REACTION RATES
    • What affects the rate of a reaction? 1. The effect of pressure in gas
      • Increase the pressure of gas
      • increases the no of particles/unit volume
      • increases the number of collisions per second .
      • Increase the rate of reaction .
      • Increase the number of effective collisions .
    • 4. Catalyst Often a catalyst is there to provide a favourable surface for a reaction to take place What affects the rate of a reaction? The black object represents the catalyst
      • A catalyst will change the rate of a reaction. - The catalyst itself does not take part in the reaction - It is not changed by the reaction
      • it is not used up during the reaction. - A catalyst is usually a transition metal, a transition metal oxide
      Properties of Catalysts
    • Examples CATALYSTS ON REACTION RATES Reaction catalyst Decomposition of hydrogen peroxide Manganese (IV) oxide, MnO 2 Manufacture of ammonia by the Haber Process Iron Contact Process to make sulphuric acid Vanadium (V) oxide, V 2 O 5
    • What affects the rate of a reaction? 1. The effect of catalyst
      • Catalyst provides alternative route
      • That has a lower activation energy
      • Increase the rate of reaction .
      • So more particles have energy equal or
      • greater than activation energy .
      • Number of effective collisions increase .
    • 4. Catalyst How does a catalyst work? 1) A catalyst provides a surface on which the reaction can take place. This increases the number of collisions between the particles of the substances that are reacting. What affects the rate of a reaction?
    • How does a catalyst work?
    • How does a catalyst work?
    • 4. Catalyst How does a catalyst work? 2) A catalyst lowers the activation energy This means that the particles can react with less energy than they needed before the catalyst was added. (Think about it: if the government lowered the legal age to buy cigarettes , then more people could legally buy cigarettes. Similarly, if we lower the amount of energy needed for particles to react, then more particles can react ). What affects the rate of a reaction?
    • A catalyst provides an alternative route for the reaction. That alternative route has a lower activation energy. Activation energy
    • Activation energy Activation energy with no catalyst Activation energy with catalyst
    • What is ? Effective collision? Collision theory? Factors affecting? Activation energy? Energy level diagram? Rate of reaction
    • In an exothermic reaction, reactants have a higher energy level than the products. Energy level diagram
    • In endothermic reactions the reactants have a lower energy level than the products. Energy level diagram
    • End of slides