Question

Carbon has two stable isotopes; 12C (98.93%) and 13C (1.07%). How many atoms of 13C would there be in a 2.05 g sample of carbon dioxide?

Answer 1

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Answer 2

Answer:

There are $1.0161\times 10^{21}$ atoms of 13-C present in a 2.05 grams sample of carbon dioxide.

Explanation:

Percentage of 12-C isotope = 98.93%

Percentage of 13-C isotope = 1.07%

Mass of the sample of carbon dioxide = 2.05 g

Mass of 13-C in the sample = 1.07% of 2.05 g

$=\frac{1.07}{100}\times 2.05 g=0.021935 g$

Molar mass of 13-C isotope = 13 g/mol

Moles of 13-C = $\frac{0.021935 g}{13 g/mol}=0.001687 mol$

$1 mol = 6.022\times 10^{23}$ atoms/ molecules

Atoms of 13-C in 0.001687 moles:

$0.001687 \times 6.022\times 10^{23}=1.0161\times 10^{21}$ atoms

There are $1.0161\times 10^{21}$ atoms of 13-C present in a 2.05 grams sample of carbon dioxide.