Physical Constants
 
 
Other Units
 
Important Equations
 
 
R    = 8.314 J mol-1 K-1
     = 0.08206 L atmK-1 mol-1
   = 0.08314 L bar K-1 mol-1
 
NA = 6.022 x 1023 mol-1
 
kB    = 1.381 x 10-23 J K-1
 
h    = 6.626 x 10-34 J s
 
F    = 96,500 C mol-1
 
c    = 2.998 x 108 m s-1
 
g    = 9.81 m s-2
 
B    = 0.51mol-1/2dm3/2
(in H2O, 25oC)
 
 
 
Sequential reactions:
 
 
[B]=(k1/(k2-k-1)) f(t)[A]0
 
 
f(t)=exp(-k1t)-exp(-k2t)
 
 
 
Parallel reactions:
 
Φi = ki/S
 
Where S is the sum of all rate constants of the paral-lel reactions
Note:
Quantum yield/efficiency = Φ = moles of product formed / moles of photons absorbed
 
1dm3   = 1 L
 
1dm3   = 1000 cm3
 
1 J    = 1 kg m2 s-2
 
1 atm    = 1.101325 x 105 Pa
 
1 atm    = 760 mmHg
 
1 Torr = 1 mmHg
 
1 Torr = 133.322 Pa
 
1 bar    = 105 Pa
 
1 nm    = 10-9 m
 
 
 
Eyring equation:
 
k =kBT/(hc0) x f
 
f =exp(ΔS#/R) x
 
x exp(-ΔH#/RT)
 
 
 
ln(1 - θ) = -θ
if θ << 1
 
 
E   = hυ
 
c   =υλ
 
PV =nRT
 
ΔG = ΔH - TΔS
 
k = A
 
k    =
 
A = e (kBT/h) exp (Δ‡S/R)
k    =
 
Ea = Δ≠Ho-PΔ≠Vo + RT (sol)
   = Δ≠Ho-ΣνRT + RT (gas)
 
log k = log ko+ 1.02 zAzB
 
log k = log ko -
ΔGo = - RT ln Kc
 
υ =

θ = KP/(1 + KP), at T=const
 
tf = (kf +kq[Q])-1,    Q is quencher
 
 
 
 
 
 



1.
Find the correct choice: The Transition State in a reaction …
A.
… must have at least one weak bond.
B.
… can have only strong bonds.
C.
… is a stable molecule.
D.
… is at a minimum of the potential energy diagram.
E.
… is a stable intermediate.


2.
At equilibrium,
A.
forward and backward reaction rates are equal.
B.
all rates are zero.
C.
the backward reaction is faster than the forward reaction.
D.
forward and backward rates are not equal.
E.
reactant concentrations are zero.


3.
For the parallel reactions
A → B
A → C
A → D
rate constant k1
rate constant k2 = 2.3 k1
rate constant k3 = 4.0 k1

What is the yield of C?
A.
31.5%
B.
13.7%
C.
54.8%
D.
45.2%
E.
86.3%


4.
Two reactions follow the Arrhenius law and have the same pre-exponential factor. If the activation energy of reaction (1) is 20 J/mol and that of reaction (2) is 200 J/mol, what would be their rate constant ratio (k1/k2) at 300K?
A.
1.075
B.
0.930
C.
1.083
D.
0.922
E.
1.037


5.
For the reaction mechanism
A → I
I → P
rate constant k1
rate constant k2

the steady state approximation yields
A.
k1[A] – k2[I] = 0
B.
k1[A] + k2[I] = 0
C.
k1[A] = 0
D.
k2[I] = 0
E.
d[P]/dt = k2[I]


6.
In the mechanism,
(1)      2{ N2O5
(2)          NO2 + NO3
(3)          NO + NO3
→
→
NO2 + NO3}
NO + O2 + NO2
2 NO2
equilibrium
 

for the decomposition of into and ,
A.
both and are intermediates.
B.
only is an intermediate.
C.
only is an intermediate.
D.
only is a catalyst.
E.
both and are catalysts.


7.
A possible mechanism for the reaction, 2A + B     C + D, is:
A + A     A2
fast, equilibrium
A2 + A   A3
slow
A3 + B   A + C + D
Fast

According to this mechanism, the rate law (rate of formation of one of the final products) will be (k is an effective rate constant keff):
A.
Rate = k[A] 3
B.
Rate = k[A][B]
C.
Rate = k[A] 2 [B]
D.
Rate = k[A]
E.
Rate = k[A ] 2


8.
The decomposition of hydrogen peroxide (substrate ) is catalyzed by the enzyme catalase (). At an initial catalase concentration [So] of the variation of (the reciprocal of the initial rate) with (the reciprocal of the initial concentration of the substrate) is given by (Lineweaver-Burk equation),
(1/R0) = 0.6977 s (1/[S]0) + 26.557 s/M

based on this experimental result, which one of the following choices is correct?
(left to right: Maximum rate in M/s, Michaelis constant in M, and the turnover number in 1/s)
A.
3.77 x 10-2,      2.63 x 10-2,      1.08 x 107
B.
2.63 x 10-2,      3.77 x 10-2,      7.51 x 106
C.
0.6977,            26.557,           1.08 x 107
D.
26.557,            0.6977,           1.08 x 107
E.
3.77 x 10-2,      2.63 x 10-2,     7.51 x 106


9.
The adsorption of Kr on charcoal at 193.5 K , closely follows the Langmuir adsorption isotherm and in turn the linear relation,

(1/Vads) = 0.34076 (torr g/cm3) x (1/P) + 0.03258 g/cm3
where is the volume of Kr adsorbed per gram charcoal at the equilibrium Kr pressure,. Which one of the following choices is correct (left to right: Volume of Ar needed to form a monolayer per gram charcoal, , and the adsorption equilibrium constant in torr-1 at 193.5 K)?
A.
30.7,              9.56 x 10-2
B.
30.7,              2.93
C.
2.93,              30.7
D.
28.7,              0.341
E.
9.56 x 10-2,    28.7


10.
The mechanism suggested for the reaction,
2 A + B → 2 C
is,
   A + A   I
forward rate constant k1, backward rate constant k-1
    I + B    → 2 C
constant k2

The rate law obtained on applying the steady state approximation is,
A.
Rate = k1k2[A]2[B]/(k-1 + k2[B])
B.
Rate = k1k2[A]2/(k-1 + k2[B])
C.
Rate = k1k2[A]2[B]
D.
Rate = k1k2[A]2[B]/(k1 + k2[B])
E.
Rate = k1k2[A][B]


11.
Using the following graphs, which one shows the rate of change of H2O2 with time (assume the reaction to be an elementary one)?
2 H2O2(l) → 2H2O(l) + O2(g)
A.
B.
C.
D.


12.
Consider the following reaction:
C2H8(g) + 4O2(g) → 2CO2(g) + 4H2O(g)

If 1.0 mol C2H8 is consumed in 4.0 min, the rate of H2O production in mol/min is
A.
1.0
B.
4.0
C.
0.25
D.
4.0
E.
8.0


13.
A second order reaction with initial reactant concentration of 0.80 M has a rate constant of 0.05 M-1s-1. How long will it take in seconds for the reactant to lose 50% of the initial concentration?
A.
25
B.
50
C.
10
D.
125
E.
8


14.
Consider the following reaction:

The relationship of the rate of appearance of B and the rate of disappearance of A is:
(Δ[B]/Δt) = C x {- Δ[A]/Δt)}
The factor C is
A.
+0.667
B.
-2/3
C.
+0.334
D.
+1
E.
+3/2


15.
Determine the rate expression for the following reaction:
2MnO4-(aq) + 6H+(aq) + 5ClO3-(aq) → 2Mn2+(aq) + 3H2O(l) + 5ClO4-(aq)
[MnO4-]/M
[ClO3-]/M
[H+]/M
Initial Rate Ms-1
0.10
0,10
0.10
5.2x10-3
0.25
0.10
0.10
3.3x10-2
0.10
0.30
0.10
1.6x10-2
0.10
0.10
0.20
7.4x10-3
 
A.
k[MnO4-]2[ClO3-][H+]1/2
B.
k[MnO4-][ClO3-] 1/2 [H+]2
C.
k[MnO4-]1/2[ClO3-][H+]2
D.
k[MnO4-][ClO3-][H+]2
E.
k[MnO4-]2[H+]1/2


16.
The mechanism of the chain reaction C2H6 → C2H4 + H2 is:

The reactive intermediates of the mechanism are the species:
A.
H, CH3 and C2H5
B.
H, CH4 and C4H10
C.
H, CH3 and C4H10
D.
CH3, CH4 and C2H5
E.
H, CH4 and C2H5


17.
The gas-phase chain mechanism of the reaction Cl2 + CH4 → CH3Cl + +HCl is:

The overall rate of reaction in terms of the rate of formation of HCl is (keff: is an effective rate constant)
A.
keff [Cl2]1/2[CH4]
B.
keff [Cl2][CH4]1/2
C.
keff [Cl2]1/2[CH3Cl]
D.
keff [Cl2] [CH3Cl]1/2
E.
keff [CH4][CH3Cl]


18.
If τf = 1 x 10-10 s and kic = 5 x 108 s-1, what is Φf? Assume that the rate constants for intersystem crossing and quenching are sufficiently small that these processes can be neglected.
A.
0.95
B.
0.81
C.
0.62
D.
0.27
E.
0.77


19.
The chlorination reaction of ethane (Cl2 + H3CCH3 ◊ ClH2CCH2Cl + H2) processes via a chain reaction mechanism. Which one of the following is not a chain propagation reaction in the chlorination of ethane?
A.
Cl + Cl             Cl2
B.
Cl + H3CCH3 ClH2CCH3 + H
C.
Cl + H3CCH3 H3CCH2 + HCl
D.
H + Cl2             HCl + Cl
E.
Cl2 + H2CCH3 ClH2CCH3 + Cl


20.
A reactant can be photo-chemically converted to a cis-product. In an experiment, 4.15 mmol of reactant are converted when irradiated with 100. W of 280. nm light for 27.0 s. All of the light is absorbed by the sample. What is the overall quantum yield for this photochemical process?
A.
0.66
B.
0.40
C.
0.10
D.
0.78
E.
0.21


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