Question

A helium balloon contains 0.26 g of helium. How many moles of helium does it contain?

Answer 1

...........1 mole
0.26g He * ------- = 0.065 moles He
...........4.0026g

(you divide how many grams you have by the atomic mass [which is the # below the element symbol on the periodic table])

Answer 2

(Sorry about the spacing, the formatting gets messed up when you post a message)

Answer 3

Yes, spacing is a problem. We work around it by doing it this way.
# mols = g/molar mass.
# mols = 0.26/4.00 = ??