Here's how to calculate the number of moles in 0.12g of helium:

1. Find the molar mass of helium:

* The molar mass of helium (He) is approximately 4.003 g/mol. This means that one mole of helium weighs 4.003 grams.

2. Use the formula:

* Moles = mass / molar mass

3. Plug in the values:

* Moles = 0.12 g / 4.003 g/mol

4. Calculate:

* Moles ≈ 0.03 mol

Therefore, there are approximately 0.03 moles in 0.12 grams of helium.