Reaction Rate
+
2H
+
-2
O
→ H2O
+
4K
+
4C
→ K4C
H2O →
+
2H
+
-2
O
Cs4Pb → 4Cs+ + Pb4-
3+
2Al
+ 3Ag2S →
2+
Al2S3 + 6Ag
2Al
3+
+ 3Ra2S →
Al2S3 + 6Ra
2+
HCl + NaOH→
→ NaCl + H2O
3BaCl2 + 2H3PO4 →
Ba3(PO4)2 + 6HCl
C3H8 + 5O2→ 3CO2 + 4H2O
C6H12O6 + 6O2 →
6CO2 + 6H2O
CuO + H2 → Cu + H2O
Rate Law
The mathematical
relationship between the rate
of a chemical reaction at a
given temperature and the
concentration of reactants.
Molarity
moles/L =M
Reaction Rate
The change in
concentration of a reactant
or product per unit time,
generally calculated and
expressed in moles per liter
per second. (mol/sL) or
(M/s)
Average rate = ∆quantity/∆t
CO + NO2 → CO2 + NO
NO at t1 = 0.000 M and 0.00s
NO at t2 = 0.010 M and 2.00s
[0.010M – 0.000M] ÷ [2.00s –
0.00s] = 0.0050 M/s
CO + NO2 → CO2 + NO
CO2 at t1 = 0.000 M and 0.00s
CO2 at t2 = 0.030 M and 4.00s
[0.030M – 0.000M] ÷ [4.00s –
0.00s] = 0.0075 M/s
Factors which influence
reaction rate
• Concentration
• Surface Area
• Temperature
• Catalyst
• Inhibitor
Catalyst
A substance that increases
the rate of a chemical
reaction by lowering
activation energies but is not
itself consumed in the
reaction.
Heterogeneous Catalyst
A catalyst that exists in
a different physical
state than the reaction
it catalyzes.
Homogeneous
Catalyst
A catalyst that exists in
the same physical
state as the reaction it
catalyzes.
Inhibitor
A substance that
slows down the
reaction rate of a
chemical reaction or
prevents a reaction
from happening.
Specific Rate Constant
A numerical value that
relates reaction rate
and concentration of
reactant at a specific
temperature.
Rate = k[A]
Reaction Order
For a reactant,
describes how the rate
is affected by the
concentration of that
reactant.
aA +bB → products
m
n
Rate=k[A] [B]
Method of Initial Rates
Determines the reaction
order by comparing the initial
rates of a reaction carried
out with varying reactant
concentrations.
2NO + 2H2 → N2 + 2H2O
Experimental Initial Rates for
aA + bB → products
Trial Initial [A] (M) Initial [B] (M) Initial Rate (M/s)
1
0.100
0.100 2.00 X 10-3
2
0.200
0.100 4.00 X 10-3
3
0.200
0.200 16.0 X 10-3
2NO + 2H2 → N2 + 2H2O
According to the table, from
trial 1 to trial 2, as [A] doubles,
so did the final. This causes
the order to become 1.
2NO + 2H2 → N2 + 2H2O
According to the table, from
trial 2 to trial 3, as [B]
doubles, the final increased
by a multiple of four. This
causes the order to become
2.
Rate =
Rate =
1
2
k[A] [B]
1
2
k[NO] [H2]
Experimental Initial Rates for
aA + bB → products
Trial Initial [A] (M) Initial [B] (M) Initial Rate (M/s)
1
0.100
0.100 2.00 X 10-3
2
0.200
0.100 2.00 X 10-3
3
0.200
0.200 4.0 X 10-3
According to the table,
from trial 1 to trial 2, as [A]
doubled, the final did not
change. This gave an
order of 0.
According to the table,
from trial 2 to 3, as [B]
doubled, so did the final.
This gave an order of 1.
Rate =
0
1
k[A] [B]
Rate = k[B]
2OH
ClO3
2ClO2 +
→
ClO2 + H2O
+
Experimental Initial Rates for
aA + bB → products
Trial Initial [A] (M) Initial [B] (M) Initial Rate (M/s)
1
0.050
0.200 6.9
2
0.100
0.200 27.6
3
0.100
0.100 13.8
2OH
ClO3
2ClO2 +
→
ClO2 + H2O
+
According to the table, from
trial 1 to trial 2, as [A]
doubled, the final increased
by a multiple of four. This
gave an order of 2.
2OH
ClO3
2ClO2 +
→
ClO2 + H2O
According to the table,
from trial 2 to 3, as [B]
halved, so did the
final. This gave an
order of 1.
+
Rate =
Rate =
2
1
k[A] [B]
2
1
k[ClO2] [OH ]
Instantaneous Rate
The rate of decomposition at
a specific time, calculated
from the rate law, the specific
rate constant, and the
concentrations of all the
reactants.
You can find the
instantaneous rate by
multiplying k (which is
given to you) by the
concentration of each
reactant after you find
each reactant’s order.
2NO + 2H2 → N2 + 2H2O
-5
X10
-1
s
k=1.0
Rate = k[NO]1[H2]2
1
2
Rate = k[0.030M] [0.04M]
Rate=1.0X10-5s-1 (0.03M)
(0.04M)2
Rate=4.8X10-10 M/s
Complex Reaction
A chemical reaction
that consists of two or
more elementary
steps.
Reaction Mechanism
The complete
sequence of
elementary steps that
make up a complex
reaction.
Intermediate
A substance produced in
one elementary step of a
complex reaction and
consumed in a subsequent
elementary step. It does not
appear in the final equation.
Rate-determining Step
The slowest
elementary step in a
complex reaction;
limits the
instantaneous rate of
the overall reaction