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Byju's Answer
Standard XII
Chemistry
Introduction to Imperfections in Solids
In a sample o...
Question
In a sample of pitch blende, the atomic ratio of
P
b
206
:
U
238
is
0.23
:
1
. Calculate the age of mineral if half life of uranium is
4.5
×
10
9
y
e
a
r
. All lead originated from uranium.
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Solution
t
=
2.303
0.693
×
t
1
/
2
×
l
o
g
⎛
⎜ ⎜ ⎜
⎝
1
+
23
/
206
1
238
⎞
⎟ ⎟ ⎟
⎠
t
=
2.303
0.693
×
4.5
×
10
9
×
l
o
g
(
1
+
0.263
)
t
=
15
×
10
9
years
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0
Similar questions
Q.
92
U
238
by successive radioactive decays changes to
82
Pb
206
. A sample of uranium ore was analyzed and found to contain 1.0 g of
U
238
and 0.1 g of
P
b
206
. Assuming that all the
P
b
206
had accumulated due to decay of
U
238
, find out the age of the ore. (Half life of
U
238
=
4.5
×
10
9
y
e
a
r
s
)
Q.
A sample of pitch blend is found to contain 50% uranium and 2.425% lead. Of this lead only 93% was
P
b
206
isotope. If the disintegration constant is
1.52
×
10
−
10
y
r
−
1
, the age of pitch blend deposits could be :
Q.
On analysis, a sample of uranium ore was found to contain
0.277
g
of
82
P
b
206
and
1.667
g
of
92
U
238
. The half life period of
U
238
is
4.51
×
10
9
yrs. If all the lead were assumed to have come from decay of
92
U
238
, what is the age of the earth?
Q.
A sample of
U
238
(half life
=
4.5
×
10
9
year), ore is found to contain
23.8
g
of
U
238
and
20.6
g
of
P
b
206
The age of the ore is
X
×
10
9
year. Calculate the value of
2
X
:
Q.
In a uranium ore the ratio of
U
238
to
P
b
206
nuclei is 1:15. Evalute the age of ore, assuming
P
b
206
to be the final, initially only uranium was present (given ratio is of number of nuclei).
(Half life=
4.5
×
10
9
years)
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