Question

How many grams of methane contain as many hydrogen atoms as there are in 4 grams of hydrogen gas​

Answer 1

Number of atoms of hydrogen present in one H₂ molecule is 2.

Molecular weight of one H₂ molecule is 2u.

So 4u H₂ will contain 2 H₂ molecules or 4 hydrogen atoms.

Hence, 4 grams of hydrogen gas will contain $4N_A$ atoms of hydrogen, where $N_A$ is then avogadro number.

1 molecule of CH₄ contains 4 hydrogen atoms.

Molecular weight of CH₄ is 16u.

So, 16 grams of CH₄ must contain $4N_A$ atoms of hydrogen.

So the answer to the question is 16 grams.

That is, 16 grams of methane will contain as many hydrogen atoms as there are in 4 grams of hydrogen gas.

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