Reaction Rate PDF

Reaction Rate Chemistry Factors affecting reaction rate There are 4 factors that affect the rate of a reaction: 1. Temperature: Increasing temperature = more energy = more collisions = more reactions study question 1 Why do changes in temperature affe...

Reaction Rate Chemistry Factors affecting reaction rate There are 4 factors that affect the rate of a reaction: 1. Temperature: Increasing temperature = more energy = more collisions = more reactions study question 1 Why do changes in temperature affect reaction rate? 2. Concentration: Increasing concentration = more particles = more collisions = more reactions low concentration high concentration study question 2 What happens to the number of collisions when there is an increase in concentration? 3. Surface Area: Increasing surface area = more places to collide = more collisions = more reactions Reaction occurs only More surface area = at the surface More chance to react study question 3 1. Which has more surface area? A 1g sugar cube or 1g of granulated sugar 2. Which would react faster? 4. Pressure (gases only): Increasing pressure = particles closer together = more collisions = more reactions low pressure higher pressure Increased pressure forces particles together study question 4 1. How would you increase the rate of a gas reaction? 2. Why does increasing pressure NOT help increase the rate of a liquid reaction? Reaction mechanics A reaction can only occur if: 1. Molecules collide 2. Molecules collide with enough energy 3. Molecules collide with the correct orientation Molecules must hit hard enough in just the right place study question 5 What are the conditions at the molecular level for a reaction to occur? Measuring reaction rate Reaction rate = speed of reaction Example An explosion happens quickly Rusting happens slowly Reaction rate = change in concentration time ∆[reactants] or ∆[products] time time ∆ = change [ ] = concentration study question 6 What is the rate of reaction when 5 moles of reactant is used in 10 seconds?  Reversible reaction: X Y [X] X Y concentration rate [Y] Y X time time As concentration decreases - Rate decreases As concentration increases - Rate increases When concentration is constant - Rate is constant study question 7 Describe how rate changes as concentration changes.  Reaction pathway Reactions are not always spontaneous Activation energy = energy needed for a reaction to happen Activation energy energy reactants products time  Catalyst A catalyst increases the rate of a reaction by lowering ‘activation energy’ A catalyst is not used up in the reaction Example: a catalytic converter allows CO to react more easily with O2 to make CO2 Reaction pathway study question 9 1. In terms of ‘activation energy’, how does a catalyst increase the rate of reaction? 2. Does a catalyst affect the energy of reactants or products?  Activated transition complex Reaction with catalyst energy reactants products time study question 10 1. Which has a higher energy: Reactants or Products? 2. How does the catalyst affect the energy of the activated transition complex?