Rate equations

What are the orders of reaction?

• zero

• first

• second

What is the reaction rate equation?

rate = k [A]^x [B]^y

What is k in the rate equation?

the rate constant

What does zero order mean?

the reaction rate is not affected by changes in the conc of that reactant

What does first order mean?

the reaction rate is proportional to the conc of that reactant

What does second order mean?

the reaction rate is proportional to the conc of that reactant squared

What is the order of reaction in the rate equation?

order with respect to a given reactant is the power to which the concentration is raised in the rate equation

What is the overall order of reaction?

the sum of the powers of the concentration terms in the rate equation

What affects the value of k in the rate equation?

temperature

as temp increases so does k

What does a concentration time graph of a zero order reactant look like?

• straight line with a negative gradient

• rate does not change

What does a concentration time graph of a first order reactant look like?

• downward curve with decreasing gradient

• constant half life (t1/2)

What does a concentration time graph of second order reactant look like?

• downward curve but steeper at start than 1st order

• not constant half life

What is the half life of a reaction?

the time for half the reagent to be used up

How can k be calculated from a first order concentration time graph?

K = ln2 / half life

What does a rate concentration graph look like for a zero order reactant?

• horizontal line

• rate does not change as conc increases

What does a rate concentration graph look like for a first order reactant?

• rate is directly proportional to conc

What does a rate concentration graph look like for a second order reactant?

• upward curve with increasing gradient