1. DEPARTMENT OF NATURAL SCIENCE
DUY TAN UNIVERSITY
DEPARTMENT OF NATURAL SCIENCE
SUBJECT: CHEMISTRY

2. RATE OF A CHEMICAL REACTION
CHEMISTRY
RATE OF A CHEMICAL REACTION
2015

3. 1. Definition Reaction rate
The rate of a chemical reaction is a measure of how fast the reaction occurs.
2015

4. aA + bB → cC + dD Reaction rate Generic reaction:
The rate of a chemical reaction is measured as a change in the amounts of reactants or products divided by the change in time.
Generic reaction:
aA + bB → cC + dD
2015

5. Reaction rate Exercise 1 Answer: B The equation for a reaction is:
2NO2(g) + H2O(g) + 1/2O2(g) → 2HNO3 (g)
Which one of the following is not numerically equal to the others?
Answer: B

6. Consider the following balanced chemical equation
Reaction rate
For example
Consider the following balanced chemical equation
H2O2 (aq) + 3I- (aq) H+ (aq) → I3- (aq) + 2H2O(l)
In the first 10,0 second of the reaction, the concentration of I- dropped from 1.000M to 0,868M.
Calculate the average of the reaction rate in this time interval.
2013

7. The effect of concentration
2. The rate Law:
The effect of concentration
Consider this reaction:
aA + bB → cC + dD
Rate = k[A]m. [B]n
k: rate constant
m: the reaction order with respect to A
n: the reaction order with respect to B
m + n: the overall order
The rate law for any reaction must always be determined by experiment.

8. The effect of concentration
2. The rate Law:
The effect of concentration
For example:
2NO2(k) + F2(k) → 2NO2F(k)
Rate = k[NO2][F2]

9. The effect of concentration
2. The rate Law:
The effect of concentration
EXAMPLE
Consider the reaction and the obtained rate / concentration data:
A(aq) + B(aq) → C(aq)
[A]
[B]
rate 1
0.10
3.10-3 2
0.20
6.10-3 3

10. 3. The Effect of Temperature on Reaction Rate
The Arhenius equation
R: the gas constant (8.314 J/mol.K)
A: constant called the frequency factor
Ea : the activation energy (is an energy barrier or hump that must be surmounted for the reactants to be transformed into products)

11. Thank you