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

There are
`1.0161* 10^(21)` atoms of 13-C present in a 2.05 grams sample of carbon dioxide.

Step-by-step 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

`=(1.07)/(100)* 2.05 g=0.021935 g`

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

Moles of 13-C =
`(0.021935 g)/(13 g/mol)=0.001687 mol`

`1 mol = 6.022* 10^(23)` atoms/ molecules

Atoms of 13-C in 0.001687 moles:

`0.001687 * 6.022* 10^(23)=1.0161* 10^(21)` atoms

There are
`1.0161* 10^(21)` atoms of 13-C present in a 2.05 grams sample of carbon dioxide.