Chapter 18 Flashcards
Rate
rate = change in conc. / change in time
order
The power to which the concentration of a reactant is raised in the rate equation.
overall order
The sum of the individual orders of reactants in the rate equation: m + n.
gives overall effect of conc. of all reactants
Zero order
When the conc. of a reactant has no effect on the rate, the reaction is zero order with respect to the reactant.
- any number raised to the power zero =1
- conc. doesn’t influence rate
First order
When the rate depends on its conc. raised to the power of 1
- if A is doubled the reaction rate increases by the same factor.
Second order
When rate depends on the conc. raised to the power of two
- if A is doubled (x2) the reaction rate increases by the factor squared.
rate equation
For a reaction: A + B → C with orders m for A and n for B, the rate equation is given by: rate = k[A]^m[B]^n
Gives the mathematical relationship between the conc. of reactants and the reaction rate.
rate constant k
The constant that links the rate of reaction with the concentrations of the reactants raised to the powers of their orders in the rate equation.
overall order=0 units
mol dm^-3 s^-1
overall order = 1 units
s^-1
Overall order = 2 units
dm^3 mol^-1 s^-1
initial rate of reaction
The change in concentration of a reactant or product per unit time at the start of the reaction: t =
Continuous monitoring
continuous measurements taken during the course of a reaction.
includes :
- monitoring by gas collection
- monitoring by mass loss
- monitoring colour change
- measuring change in conc. of H+ ions with a pH meter
Colorimeter
Measures the intensity of light passing through a sample. A filter is chosen so that it is the complementary colour to the colour being absorbed in the reaction. Absorbance is directly linked to the conc. of the solution.
Concentration - time graph gradient shows?
rate of reaction
