Question

What is the mass, in grams, of a sample of 7.83 × 1024 atoms of helium (He)? Show your work or explain the steps that you used to determine your answer.

Answer 1

First, we will get the number of moles:
one mole contains Avogadro's number of atoms. Therefore, to know the number of moles in 7.83 × 10^24 atoms, we will simply do cross multiplication as follows:
number of moles = (7.83 × 10^24*1) / (6.022 * 10^23) = 13 moles

From the periodic table:
mass of one mole of helium = 4 grams
Therefore:
mass of 13 moles of helium = 13*4 = 52 grams