F325 - Rates and Equilibria Flashcards
List five factors that affect the rate of a chemical reaction.
Temperature Pressure (gas)/concentration (liquids) Surface area Catalyst Agitation (stir) Radiation pH
Define the rate of a chemical reaction.
The change in concentration of reactants or products per unit time.
Define initial rate of reaction
Is the change in concentration of a reactant, or product, per unit time at the start of the reaction when t=0
What are the units of rate of reaction?
Moldm-3s-1
How is a rate of reaction measured from a concentration-time graph?
Drawing a tangent to the curve at the required time, and the gradient of the tangent is measured
Describe a zero order concentration time graph
Concentration decreases at a constant rate. Half-life decreases with time
Describe a first order concentration time graph
The concentration halves in equal time intervals. Half-life is constant
Describe a second order concentration-time graph
Concentration decreases rapidly, but the rate of decrease then slows down. Half-life increases with time
Define half-life
The time taken for the concentration of one of the reactants to fall to half of it original value.
The half-life of a first order reaction is independent of the concentration of the reactants.
Give a general rate equation
Rate=k[A]m[B]n
Define the term rate determining step (RDS)
The slowest step in the reaction mechanism of a multi-step reaction, which determines the overall rate
Describe the two different graphs frequently plotted in rate experiments
Concentration-rate graphs; rate-concentration graphs
Define Le Chatelier’s Principle
A system in equilibrium will shift in such a way as to oppose any changes imposed upon it
What would a large value of Kc mean and what would a small value of Kc mean?
Large Kc value means the equilibrium position lies to the right; small Kc value means the equilibrium position lies to the left.
What is Kc called?
The equilibrium constant
