2007
1. Express
the rate of the following reaction in terms of disappearance of hydrogen in the
reaction
3H2(g) + N2 (g) Ã 2 NH3(g)
2. The rate constant for a first order reaction is 60 s-1 . How much time will it take to reduce the concentration of the reactant ti 1/10 th of its initial value?
2008
1. Derive the general expression for half life of a first order reaction.
2. The decomposition of NH3 on platinum surface is a zero order reaction . What would be the rates of production of N2 and H2 if k = 2.5 × 10-4 mol L-1 s-
3. List the factors that determine the rate of a chemical reaction
4. The half-life for radioactive decay of 14C is 5730 years. An archaeological artifact containing wood had only 80% of the 14C found in a living tree. Estimate the age of the sample.
5. Define order of a chemical reaction
6. A first order reaction takes 40 min for 30% decomposition. Calculate t1/2.
2009
1. Define
the following
(a)
Elementary step in a reaction
(b) Rate of a reaction
2. A first order reaction has a rate constant of 0.0051 min-1 . If we begin with 0.10 M concentration of the reactant , what conc of the reactant will be left after 3 hrs ?
3. For a
decomposition reaction the values of rate constants k at two different temp.
are given below:
k1
= 2.15 × 10-8 L mol-1
s-1 at 650 K
k1
= 2.39 × 10-7 L mol-1
s-1 at 700 K
Calculate the value of activation energy for this reaction. ( R= 8.314 J K-1 mol-1)
4. Define
the following
(a) Order
of a reaction
(b) Activation energy of a reaction
2010
1. Define
the following
(a)
Activation energy of a reaction
(b) Rate of a reaction
2. The
decomposition of phosphine PH3 proceeds according to the following
equation-
4PH3(g) Ã
P4 (g) + 6H2(g)
It is found
that the reaction follows the following rate equation :
Rate = k[PH3]
The half
life of PH3 is 37.9 sec at 120 0C
3. a) How much
time is required for ¾ th of PH3 to decompose?
b) What
fraction of the original sample of PH3 remains behind after 1 min
?3. Explain
a) Order of
a reaction
b) Molecularity of a reaction
4. The rate
of a reaction increases 4 times when the temp changes from 300 K to 320 K .
Calculate the energy of activation of the reaction, assuming that it does not
change with temp.
( R = 8.314 J K-1 mol-1)
2011
1. Define order of a reaction.
2. What do
you understand by rate law and rate constant of a reaction ? Identify the order
of a reaction if the units of its rate constants are
L-1
mol s-1
L mol-1 s-1
3. The
thermal decomposition of HCOOH is a
first order reaction with a rate constant of
2.4 × 10 -3
s-1 at a certain temp.
Calculate how long will it take to form three-fourth of its initial quantity of
HCOOH to decompose ( log 0.25 = -0.6021
)
4. A
reaction is second order w r t a
reactant . How is the rate of reaction is affected if the concentration of the
reactant is reduced to half ? What is the unit of rate constant for such
a reaction?
5. Define activation energy of a reaction
2012
1. A reaction is second order with respect to a reactant. How is the rate of reaction affected if the concentration of the reactant is (i) doubled (ii) reduced to half ?
2. The reaction , N2 (g) + O2 (g) = 2 NO (g) contributes to air pollution whenever a fuel is burnt in air at a high temp. At 1500 K , equilibrium constant K for it is 1.0 × 10-5 . Suppose in a case [N2] = 0.80 M and [O2] = 0.02 M before any reaction occurs. Calculate the equilibrium concentrations of the reactants and the product after the mixture has been heated to 1500 K
2013
(a) (a) For a reaction A + B → P, the rate law is
given by r = k[A]1/2[B]2
What is the order of this reaction ?
(a) (b) A first order reaction is found to have a rate constant k
= 5.5 × 10–14 s–1. Find the half life of the reaction.
(c ) The rate of a reaction becomes four times when
the temperature changes from 293 K to 313 K. Calculate the energy of activation
(Ea) of the reaction assuming that it does not change with temperature.
[R =
8.314 J K–1 mole–1, log 4 = 0.6021]
2014
1) For chemical reaction R ->P the variation in the concentration (R) vs. time(t) plot is given as
i)Predict the order of the reaction.
ii) What is the slope of the curve?
2) The following data were obtained during the first order thermal decomposition of SO2Cl2 at const. volume:
SO2Cl2 (g) Ã SO2(g) +Cl2 (g)
|
Experiment |
Times/s-1 |
Total
pressure/atm |
|
1 |
0 |
0.4 |
|
2 |
100 |
0.7 |
Calculate the rate
const.
|
t/s |
0 |
20 |
40 |
|
[CH3COOCH3]/molL-1 |
0.04 |
0.02 |
0.01 |
a) Show that it
follows pseudo first order reaction, as the conc of water remains constant.
2. Define the
following terms :
a) Collision frequency b) Rate constant (k)
3. The rate constant
of a first order reaction increases from 4×10-2 to 24×10-2
when the temp changes from 300 K to 350 K. Calculate the energy of activation
(Ea)
3. For the first order
thermal decomposition reaction , the following data were obtained
C2H5Cl
(g) Ã C2H4(g) + HCl(g)
Time/sec Total pressure/atm
0 0.30
300 0.50
Calculate the rate
constant
1. 1. What
is the effect of adding a catalyst on
a)
Activation
energy ( Ea) b) Gibbs energy ( ∆G) of a reaction
2. 2. A
first order reaction takes 20 minutes for 25% decomposition. Calculate the time
when 75% of the reactant will be completed.
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