Question

${}^{12}C$ and ${}^{14}C$ isotopes are found as 98% and 2% respectively any sample. Then, the number of ${}^{14}C$ atoms in 12 g of the sample will be:

• A. 1.5 mole atoms
• B. $1.032\times {10}^{22}atoms$
• C. $2.06\times {10}^{21}atoms$
• D. 2 g atoms

Answer 1

The correct option is B $1.032\times {10}^{22}atoms$

14 g of carbon 14 atom contains $=6.023\times {10}^{23}$atoms

1 g of carbon 14 atom contains $=\frac{6.022\times {10}^{23}}{14}$

12 g of carbon 14 atom contains $=\frac{6.022\times {10}^{23}\times 12}{14}$

$=5.16\times {10}^{23}$

Now its 2% is $\frac{(5.16\times {10}^{23}\times 2)}{100}$

$=10.32\times {10}^{21}$

$\therefore$ The number of C−14 atoms in 12 g of carbon is $1.032\times {10}^{22}$

Hence, the correct option is $\left(B\right)$.