Chapter 10 - Reaction Rates And Equilibrium (10.1-10.5) Flashcards
How do you work out the rate of a chemical reaction?
Change in concentration/time
What are the units for the rate of a chemical reaction?
Moldm^-3s^-1
How can you measure a rate of reaction?
By measuring the change in concentration of a reactant or a product in a given time
Describe a concentration time graph
1) At the start the rate of reaction is fastest because each reactant has a high concentration
2) Rate of reaction slows as the reaction proceeds, because the reactants are being used up, less frequent collisions
3) Once the reactants have beenh completely used up graph plateaus as rate of reaction is 0
What 4 factors can effect the rate of reaction?
Concentration, temperature, use of a catalyst, surface area of solid reactants
How does increasing the concentration or pressure affect the rate of reaction?
When the concentration is increased, the rate of reaction is increased as it increases the number of particles in the same volume and particles are closer together, so the particles will collide more frequently and there will be more effective collisions
What two methods can be used to monitor the progress of a reaction that produces a gas?
1) Monitoring the volume of gas produced at regular time intervals using gas collection
2) Monitoring the loss of mass of reactants using a balance
How can you get a value for the rate of reaction?
Plot a graph of total volume of gas produced against time. Draw a tangent at the time you need a rate of reaction for and calculate the gradient
What are the 2 major features of a catalyst?
1) The catalyst may react to form an intermediate or may provide a surface a reaction can take place on
2) At the end of the reaction the catalyst is regenerated (It is not used up in a chemical reaction)
How does a catalyst increase the rate of reaction?
It provides an alternative reaction pathway of lower activation energy
What is a homogeneous catalyst and how do they work?
It has the same physical state as the reactants, it reacts to form an intermediate then the intermediate breaks down to give the product and regenerates the catalyst
What is a heterogeneous catalyst and how do they work?
They have a different physical state to the reactants. Reactants are adsorbed (weakly bonded) onto the surface of the catalyst, where the reaction takes place then after the reaction the product molecules leave by desorption
What state are heterogeneous catalysts used in?
usually solids (gaseous or aqueous reactants)
How are catalysts sustainable?
They lower the activation energy, this reduces energy requirements and temperature of the process. This means less electricity or fossil fuel is used.
How are catalysts economically friendly?
It makes the product faster and uses less energy which cuts costs and increases profitability
Economic advantages outweigh costs associated with developing a catalyst