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# Before 1900, the activity per mass of atmosphere carbon due to the presence of 14C averaged about 0.255 Bq per gram of C. What fraction of carbon atoms were 14C? Given: Half life is 5730 years. One 14C in every 3×1012 atomsFour 14C in every 1010 atomsThree 14C in every 1012 atomsTwo 14C in every 1011 atoms

A
One 14C in every 3×1012 atoms
B
Four 14C in every 1010 atoms
C
Two 14C in every 1011 atoms
D
Three 14C in every 1012 atoms
Solution
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#### Decay constant, λ=ln2t1/2=1.209×10−4yr−1Activity is given by: dNdt=λNHence, N=dN/dtλ=6.66×1010Number of carbon atoms in 1 gm is 6×102312=5×1022Fraction of 14C is given by:6.66×10105×1022=1.33×10−12

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Similar Questions
Q1
Before 1900, the activity per mass of atmosphere carbon due to the presence of 14C averaged about 0.255 Bq per gram of C. What fraction of carbon atoms were 14C?
Given: Half life is 5730 years.

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Q2
The lowest level 14C activity for experimental detection is 0.03 dis/min -g of 14C. The activity of 14C in atmosphere is 15 dis/min-g of 14C. The maximum age of an object that can be determined by 14C method is:
(t1/2of14C=5730year)
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Q3
When charcoal is prepared from a living tree, it shows a disintegration rate of 15.3 disintegrations of 14C per gram per minute. A sample from an ancient piece of charcoal shows 14C activity to be 12.3 disintegrations per gram per minute. How old is this sample? (Half - life of 14C is 5730 years and ln0.8039=0.2182)

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Q4
A pieces of bone an animals from a ruin is found to have 14C activity of 12 disintegrations per minute per gm of its carbon content. The14C activity of of a living animal is 16 disintegration per minute per gm How long ago nearly did the animal die?
(Given half of life 14Cis t1/2=5760 years)
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Q5
A piece of bone of an animal from a ruin is found to have 14C activity of 12 disintegrations per minute per gm of its carbon content. The 14C activity of a living animal is 16 disintegrations per minute per gm. Nearly, how long ago did the animal die? (Given half life of 14C is t12=5760years)
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