Chemistry Notes Reaction Rates - calhoun.k12.al.us Notes... · Method of Initial Rates Determines...
Transcript of Chemistry Notes Reaction Rates - calhoun.k12.al.us Notes... · Method of Initial Rates Determines...
Reaction Rate
2H+ + O-2 →→→→ H2O
4K+ + C4- →→→→ K4C
H2O →→→→ 2H+ + O-2
4Cs+ + Pb4-Cs4Pb →→→→
2Al3+ + 3Ag2S →→→→
Al2S3 + 6Ag2+
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.
moles/L =M
Molarity
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.
InhibitorA 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.
Rate=k[A]m[B]n
aA +bB → products
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
16.0 X 10-30.2000.2003
4.00 X 10-30.1000.2002
2.00 X 10-30.1000.1001
Initial Rate (M/s)Initial [B] (M)Initial [A] (M)Trial
aA + bB → products
Experimental Initial Rates for
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.
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.
2NO + 2H2 → N2 + 2H2O
Rate = k[A]1[B]2
Rate = k[NO]1[H2]2
4.0 X 10-30.2000.2003
2.00 X 10-30.1000.2002
2.00 X 10-30.1000.1001
Initial Rate (M/s)Initial [B] (M)Initial [A] (M)Trial
aA + bB→ products
Experimental Initial Rates for
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 = k[A]0[B]1
Rate = k[B]
2ClO2 + 2OH- → ClO3- +
ClO2- + H2O
13.80.1000.1003
27.60.2000.1002
6.90.2000.0501
Initial Rate (M/s)Initial [B] (M)Initial [A] (M)Trial
aA + bB→ products
Experimental Initial Rates for
2ClO2 + 2OH- → ClO3- +
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.
2ClO2 + 2OH- → ClO3- +
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 = k[A]2[B]1
Rate = k[ClO2]2[OH-]1
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
k=1.0 X10-5 s-1
Rate = k[NO]1[H2]2
Rate = k[0.030M]1[0.04M]2
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