Kinetics
No description yet. This curated deck is ready for daily study.
Card preview (18)
How ca the rate of a chemical reaction be measured?
by analysing some observable property which changes as the reaction proceeds, at suitable time intervals
What does the rate of a chemical reaction depend on?
the concentration of the reactants
Reaction rates can be expressed in terms of the rate at which a particular reactant changes over time? What equation is used to express this?
Rate= -d[R]/dt
What does a plot of reaction rate vs [R] show?
that rate is directly proportional to [R]
What is the rate constant represented by?
k (must be lower case)
What does n stand for?
the order of the reaction
For a general equation A+B>C+D Write an expression for the rate equation.
R=k[A]m[B]n m and n are the orders w.r.t. A and B
What is the overall order of the reaction?
the sum of the powers to which the concentrations are raised in the rate equation.
What must the order of a reaction w.r.t. a particular reactant be deduced from?
cannot be deduced from the equation for the reaction, and must be determined experimentally.
What can the rate equation be determined from?
the initial rate data for a series of reactions in which the initial concentrations of the reactants are varied.
Describe the relationship between the reaction rate and the concentration of reactant for zero order reactions (n=0).
The reaction rate is independent of the concentration of reactant
Describe the relationship between the reaction rate and the concentration of reactant for first order reactions (n=1).
Doubling the concentration of a particular reactant will double the reaction rate
Describe the relationship between the reaction rate and the concentration of reactant for second order reactions (n=2).
Doubling the concentration of a particular reactant will quadruple the reaction rate
What are the units for rate?
mol l-1 s-1
What do most chemical reactions proceed as?
a series of simple steps rather than one single step involving all the reactants
What does the overall rate of a reaction depend on?
the slowest step in the mechanism. This is known as the rate determining step
What does the rate equation provide information about?
the rate determining step
What does the order w.r.t. a particular reactant tell us?
It tells us how many molecules of that reactant take part in the rate determining step.