To determine the number of moles in a given mass of a substance, you can use the molar mass, which is the mass of one mole of the substance.
The atomic mass unit (amu) is a unit of mass used to express atomic and molecular weights. The molar mass of helium (He) is approximately 4.00 grams per mole (g/mol).
To calculate the number of moles, you can use the following formula:
Number of moles = Mass (in grams) / Molar mass (in g/mol)
In this case, we have a mass of 54 amu for helium. However, we need to convert this mass to grams before using the formula.
Since 1 amu is approximately equal to 1.6605 x 10^-24 grams, we can convert the mass of helium from amu to grams:
Mass (in grams) = 54 amu * (1.6605 x 10^-24 g/amu)
Now, we can calculate the number of moles:
Number of moles = (54 amu * (1.6605 x 10^-24 g/amu)) / (4.00 g/mol)
Calculating this expression gives:
Number of moles ≈ 2.25 x 10^-23 mol
Therefore, there are approximately 2.25 x 10^-23 moles in a 54 atomic mass unit of helium.