A sample of diatomic gas A has three times the mass of an equal volume of gas B under the same conditions. What is the ratio of the atomic mass of A to that of B?

1 Answer
Ernest Z.
Mar 15, 2017

The atomic mass of #"A"# is 1.5 times the atomic mass of #"B"#.

Explanation:

Let's say that the formula of Gas A is #"A"_2# and the formula of Gas B is #"B"#.

Avogadro's Law tells us that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.

Thus, if Gas A has three times the mass of an equal volume of Gas B, a molecule of Gas A must have three times the mass of an atom of Gas B.

But a molecule of Gas A contains two atoms of #"A"#.

Hence each atom of #"A"# has #3/2 = 1.5# times the mass of an atom of #"B"#.

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