How many atoms of vanadium are present in #"185 mg"# of this element?

1 Answer
Stefan V.
Jan 26, 2015

The answer is #"2.19" * "10"^(21)# atoms of vanadium are in #"185 mg"#.

Since you know what the mass of 1 atom is, and you know the number of grams for which you must determine the number of atoms, this boils down to setting up a simple conversion factor:

#"185 mg" * ("1 gram")/("1000 mg") * ("1 atom")/(8.46 * 10^(-23)"g") = 2.19 * 10^(21)"atoms"#

You could double check your answer by comparing the number of atoms in #"185 mg"# to the number of atoms in 1 mole of vanadium, or #"50.9 g"#.

#"185 mg"# represents a mass about 300, or #3 * 10^2#, times smaller than #"50.9 g"#, so that's how many times less atoms you'll have compared to the number of atoms in 1 mole, #6.022 * 10^(23)#.

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