For isotopic analysis, an ice core sample was heated to produce gaseous H2O. If 3.00 μg of gaseous H2O was injected into a mass spectrometer: How many moles of water were injected? 1.67×10−7
If the sample contains 0.0156% deuterium, how many deuterium atoms were injected?

1.67 × 10⁻⁷ mol H₂O

3.14 × 10¹³ atoms deuterium

Explanation:

How many moles of water were injected?

We have 3.00 μg of gaseous H₂O. To calculate the number of moles of water we will use the following relationships:

If the sample contains 0.0156% deuterium, how many deuterium atoms were injected?

We will use the following relationships:

1 mole of water contains 6.02 × 10²³ molecules of water.

There are 2 hydrogen atoms per water molecule.

0.0156% of hydrogen atoms are deuterium atoms.