How many moles are in 20.0 g He?

1 Answer
Meave60
Apr 20, 2016

There are 5.00 moles He in 20.0 g He.

Explanation:

In order to determine the number of moles of a given mass of a substance, divide the given mass by its molar mass.

The molar mass of helium is #"4.0026 g/mol"# (atomic mass from the periodic table in g/mol).

#20.0cancel"g He"xx(1"mol He")/(4.0026cancel"g He")="5.00 mol He"# rounded to three significant figures

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