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# Solution - Rate of reaction Test - Chemical Kinetics Class 12 Notes | EduRev

## Class 12 : Solution - Rate of reaction Test - Chemical Kinetics Class 12 Notes | EduRev

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CBSE TEST PAPER-01
CLASS - XII CHEMISTRY (Chemical Kinetics)
Topic: -Rate of reaction –Average and instantaneous rates.
1. The branch of chemistry that deals with the study of reaction rates and their mechanisms is
called chemical Kinetics.
2. Rate of reaction can be defined as the change in concentration of a reactant or product per
unit time.
3. Average rate of a reaction is defined as the change in concentration of a reactant or a
product per unit time. It can be determined by dividing the change in concentration of
reactant or product by the time interval
For the reaction: A ? B R av =
[ ] [ ]
=
A B
t t
- ? ?
? ?
4. The units of rate of a reaction are Mol /L /s
5. The rate of a reaction at a particular moment of time is called instantaneous rate of a
reaction.
For a reaction A ? B
R inst =
[ ] [ ]
= .
d A d B
dt dt
Where dt = the smallest possible time interval ( 0) t ? ?
6. In terms of reactant In terms of products
i) R
1 =
[ ]
3
1
4
NH
t
?
- ?
R
3
=
[ ] 1
4
NO
t
?
?
R
2
=
[ ]
2

1
5
O
t
?
- ?
R
4
=
[ ]
2
1
6
H O
t
?
?
1 2 3 4
1 1 1 1
R =  R =  R =  R
4 5 4 6
[ ] [ ] [ ] [ ]
3 2 2
1 1 1 1
= -  =  =
4 5 4 6
NH O NO H O
t t t t
? ? ? ?
- ? ? ? ?
Page 2

CBSE TEST PAPER-01
CLASS - XII CHEMISTRY (Chemical Kinetics)
Topic: -Rate of reaction –Average and instantaneous rates.
1. The branch of chemistry that deals with the study of reaction rates and their mechanisms is
called chemical Kinetics.
2. Rate of reaction can be defined as the change in concentration of a reactant or product per
unit time.
3. Average rate of a reaction is defined as the change in concentration of a reactant or a
product per unit time. It can be determined by dividing the change in concentration of
reactant or product by the time interval
For the reaction: A ? B R av =
[ ] [ ]
=
A B
t t
- ? ?
? ?
4. The units of rate of a reaction are Mol /L /s
5. The rate of a reaction at a particular moment of time is called instantaneous rate of a
reaction.
For a reaction A ? B
R inst =
[ ] [ ]
= .
d A d B
dt dt
Where dt = the smallest possible time interval ( 0) t ? ?
6. In terms of reactant In terms of products
i) R
1 =
[ ]
3
1
4
NH
t
?
- ?
R
3
=
[ ] 1
4
NO
t
?
?
R
2
=
[ ]
2

1
5
O
t
?
- ?
R
4
=
[ ]
2
1
6
H O
t
?
?
1 2 3 4
1 1 1 1
R =  R =  R =  R
4 5 4 6
[ ] [ ] [ ] [ ]
3 2 2
1 1 1 1
= -  =  =
4 5 4 6
NH O NO H O
t t t t
? ? ? ?
- ? ? ? ?
II ) In terms of reactant  In terms of product
R1 =
[ ]
2 5

N O
t
?
- ?
[ ]
2
2
=
NO
R
t
?
?
[ ]
2
3
=
O
R
t
?
?
1 2 3
1 1
=  = R
2 2
R R -
[ ] [ ] [ ]
2 5 2 2
1
=   =
2
N O NO O
t t t
? ? ?
? ? ?
7. Rate of reaction =
change in concentration
time interval
=
(0.8420 0.2105) mol/L
2hr
- =
0.6315
= 0.3158 mol /L/hr
2
.
8. While writing the expression for rate of a reaction is terms of reactants, there is a negative
sign which indicates a decrease in concentration of reactants with time.
9. From the equation 2O
3
(g)
-- ?
?- - 3O
2
(g)
[ ] [ ]
3 2
1 1
=
2 3
O O
t t
? ?
- ? ?
[ ] [ ]
2 3
3
=
2
O O
t t
? ?
- ? ?
=
-4 -1
3
(-5.0 10 atms )
2
- × × =
4 -1
7.5 10 atms
- ×
10. 2A     ? 4B +C
[ ] [ ] [ ] 1 1
=   =
2 4
d A d B d C
dt dt dt
- i) Rate of disappearance of B
=
3
1
5 10
mol /L
10 5
- - ×
=
-4 -1 -1
5 10 mol L  s ×
ii)
[ ] [ ] [ ] d
2 1
=   =
4 2
A d B d B
dt dt dt
- =
4 -1 -1
1
5 10 mol L s
2
- × × = 2.5
4 -1 -1
10 mol L s ×
```
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