Question

# The isotopic abundance of C-12 and C-14 is 98% and 2% respectively. What would be the number of C - 14 isotope in 12 g carbon sample?

A
1.032×1022
B
3.01×1023
C
5.88×1023
D
6.02×1023

Solution

## The correct option is D $$1.032\, \times\, 10^{22}$$Isotopic abundance of $$C-12$$ is $$98$$%Isotopic abundance of $$C-14$$ is $$2$$%Average atomic mass $$= \cfrac {Mass \ number \times Relative \ abundance \ + \ Mass \ number \times Abundance}{100}$$$$= \cfrac {98 \times 12 + 2 \times 14}{100}$$$$=12.04 \ grams$$So, in $$100$$ grams of carbon sample, $$C-14$$ isotope will be $$2$$ grams since it is $$2$$% in abundance.$$\therefore$$ in $$12$$ grams sample, $$C-14$$ isotope will be $$=\cfrac {12 \times 2}{100}=0.24 \ grams$$$$1$$ mole of any compound has $$N_A$$ number of atoms i.e $$6.02 \times 10^{23}$$. So, $$C-14$$ isotope will be $$1.032 \times 10^{22}$$Chemistry

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