Chem 111
HW Key #1
Sept 4, 2009
A.26:
E
k
= ½ mv
2
= ½(2.5 x 10
5
kg)(25 km·s
1
)
2
(1000 m/1 km)
2
= 7.8 x 10
13
kg · m
2
· s
2
= 7.8 x 10
13
J
A.29:
E
P
= mgh
= (40.0 g)(9.81 m · s
2
)(0.50 m)(1 kg/1000 g)
= 0.20 kg · m
2
· s
2
for one raise of a fork
For 30 raises, (30)( 0.20 kg · m
2
· s
2
) = 6.0 J
A.30:
A.33:
The relationship between distance of separation and potential energy for charged
particles is given in section A.2, equation 4.
Considering the proton and electron beginning at rest and at infinite separation
sets the initial total energy to 0.
Since the electron is not at rest in a hydrogen
atom, its total energy is represented by equation 5: E = E
k
+ E
P
.
We have only
calculated the potential energy.
The discrepancy between the calculated value of
the potential energy, 27.7eV, and the measured amount released, 13.6 eV, is the
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 Fall '08
 Owens,G
 Atom, Energy, Kinetic Energy, Potential Energy, Electric charge

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