Rate of chemical reactions Flashcards
1
Q
What is rate of reaction?
A
- change in conc (of any reactants or products) per unit time
2
Q
From a graph of conc over time how do u find the rate of reaction at a partciular time?
A
draw a tangent
find its gradient
3
Q
What does the rate of reaction depends on?
A
- the conc of some or all of the species in the reaction vessel
- reacatants and catalyst
- these do not make the same contribution
4
Q
What does the rate expression tell us?
A
the contribution of the species that affect the rate
5
Q
What does the equation rate ∝ [X] [Y] tell us?
A
- [X] and [Y] have equal effect on rate
- doubling either would double the rate of the reaction
- doubling both would quadruple the rate
6
Q
What is the rate constant?
A
- introducing rate constant allows you to get rid of proportionality sign
- rate = k [X] [Y]2
- k
- different for every reaction and varied with temperature
- conditions needed to be stated
7
Q
Wgat is the rate = to when all species in the rate equation are 1 mol dm-3
A
- = to the value of k
- e.g.
- K x 1 x 1 x 12 = K
8
Q
What is the order of reaction?
A
- order of reaction with respect to one of the species, is the power to which the conc of that species is raised in the rate expression
- it tells how the rate depends on the conc of that species
- e.g. rate = k [X] [Y]2
- X is one [X]1 = [X]
- Y is 2
- as conc of Y doubles the rate quadruples
9
Q
What is the ovarall order of the reaction?
A
- sum of all the individual orders
10
Q
What is the general rate expression?
A
- rate = k [A]a [B]b
- a = order with respect to A etc
11
Q
What is the link between the chemical equation and the rate expression?
A
- coefficeint of a species (number in front of it has no affect)
- catalyst, not involved in chemical equation, may appear in the rate expression
