Tardigrade
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Tardigrade
Question
Chemistry
The standard enthalpy of formation (ΔfHo298) for methane, CH4 is -74.9 kJ mol-1. In order to calculate the average energy given out in the formation of a C — H bond from this it is necessary to know which one of the following ?
Q. The standard enthalpy of formation
(
Δ
f
H
298
o
)
for methane,
C
H
4
is
−
74.9
k
J
m
o
l
−
1
. In order to calculate the average energy given out in the formation of a C — H bond from this it is necessary to know which one of the following ?
2704
211
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JEE Main 2014
Thermodynamics
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A
the dissociation energy of the hydrogen molecule,
H
2
13%
B
the first four ionisation energies of carbon
4%
C
the dissociation energy of
H
2
and enthalpy of sublimation of carbon (graphite)
67%
D
the first four ionisation energies of carbon and electron affinity of hydrogen
16%
Solution:
To calculate average bond energy of
(
C
−
H
)
bond, dissociation energy of
H
2
and enthalpy of sublimation of carbon (graphite) is needed.
