3.1.9 Rate Equations Flashcards
Rate of reaction
Shows how fast reactants are converted to products. It depends on the concentrations of the reactants and the rate constant.
Rate equation (explain)
Describes the relationship between the rate of chemical reaction and concentrations of the reactants
Rate equation (state general equation)
Rate = k[A]m [B]n
Order of reaction
Tells you how the reactant concentration will affect the rate of reaction. In a rate equation, it is the appropriate power to which the concentration of the reagent is raised.
Overall order of reaction
Sum of all the individual orders of the reactants in a chemical reaction.
Concentration - time graph
A graph which can be used to deduce the rate of reaction by drawing a tangent of the curve.
Describe the shape of the conc-time graphs for:
- 0 order
- 1st order
- 2nd order
0 order
- straight line, linear, down
1st order
- decelerating curve
2nd order
- steeper, finishes earlier, decelerating curve
Rate - concentration data
Rate-concentration data or graphs can be used to deduce the order (0, 1 or 2) with respect to a particular reactant.
Describe the shape of the rate-conc graphs for:
- 0 order
- 1st order
- 2nd order
0 order
- straight line, constant, across, gradient = 0
1st
- directly proportional line going upwards
2nd
- non-linear curve upwards (accelerating)
Rate constant
Relates the rate of a chemical reaction at a given temperature to the product of the concentrations of reactants.
(k)
units of k depend on rearranging the rate equation
Concentrations do not always affect rate (0 order), why not?
- In any mechanism, species that are only involved in steps after the RDS do not appear in the rate equation.
- However, species that appear in the steps up to, and including, the RDS are in the rate equation.
Rate determining step
The slowest step in a multi-step reaction. The overall rate is decided by this step since species occurring in and up til the RDS will also occur in
What is the Isolation method?
Allows us to determine how the rate of reaction is affected by the concentration of one of the reactants.
How is the isolation method done?
The dependence of the reaction rate on the chosen reactant concentration is isolated by having all other reactants present in a large excess, so that their concentration remains essentially constant throughout the course of the reaction.
What’s the point of the Isolation method?
This greatly simplifies the rate law since the (constant) concentrations of all reactants present in large excess may be combined with the rate constant to yield a single effective rate constant.
