LT#4: Reaction Rates Flashcards
What is the equation for determining the rate of a reaction?
Ave Rate = ∆mol/∆time
OR
Ave Rate = ∆M/∆time
If you calculate the reaction rate in one chemical, how do you change it into another chemical?
Times by a mole ratio
Describe how tracking the mass of an experiment can be used to determine the rate of a reaction.
If your reaction produces a gas, the loss of mass can be observed in an open container on an electronic balance. Use m = nxM to find moles of gas made, then divide by time to get rate.
Describe how tracking the pressure of an experiment can be used to determine the rate of a reaction.
If your reaction produces a gas, a pressure increase can be observed in a closed container with a pressure gauge. Use PV = nRT to find moles of gas made, then divide by time to get rate.
Describe how tracking the volume of a gas can be used to determine the rate of a reaction.
If your reaction produces a gas, it can be collected through downward displacement of water and its volume measured. Use PV = nRT to find moles of gas made, then divide by time to get rate.
Describe how tracking the pH of an experiment can be used to determine the rate of a reaction.
Recoding pH changes with a pH probe measures the consumption or production of an acid or base. Use pH =-log[H3O+] to find moles of acid/base then divide by time to get rate.
Describe how tracking the electrical conductivity of an experiment can be used to determine the rate of a reaction.
If the reactants and products have different quantities of dissolved ions, this will cause a change of conductivity. This can be measured with a voltmeter/ammeter.
Describe how tracking the colour of an experiment can be used to determine the rate of a reaction.
If one of the chemicals in the reaction has a distinctive colour, you can use a spectrophotometer to track the change in colour intensity. There is a direct relationship between absorption of light due to colour and chemical concentration. Use this relationship to determine the change in moles of this chemical, then divide by time to get rate.
List the conditions necessary for reactants to have a successful collision.
Must collide at proper orientation with the correct amount of activation energy. Even when this occurs only 50% of the activated complex turns into reactants.
Define the term Transition state
Point in reaction when reactants change into products. Activated complex (mixture of reactants and products with temporary bonds) exists at this state.
Where on an energy diagram is delta H?
Difference in energy between reactants and products.
Where on an energy diagram is Ea(fwd)?
Difference in energy between reactants and transition state.
Where on an energy diagram is Ea(rev)?
Difference in energy between products and transition state.
How does changing the concentration of the reactants influence the reaction’s rate?
Increasing the concentration (more particles in the same volume) of one or more reactants increases the number of collisions that occur per unit of time.
This increases the probability that a successful collision will occur.
How does changing the surface area of the reactants influence the reaction’s rate?
Adding solid reactants as powders (high surface area) increases the number of reactant particles that are available to collide.
This increases the number of collisions per unit of time and the probability that a successful collision will occur.
