# Question #071e5

Jul 5, 2015

#### Answer:

Because a hydrogen molecule contains two hydrogen atoms.

#### Explanation:

A hydrogen molecule, ${\text{H}}_{2}$, is formed when two hydrogen atoms, $\text{H}$, share their respective electron to form a covalent bond. If a hydrogen molecule contains two hydrogen atoms, then its mass will be twice as big as that of an individual hydrogen atom.

A mole simply represents a collection or molecules or atoms. A substance's molar mass tells you how much one mole of that substance weighs.

In your case, one mole of hydrogen molecules will be twice as heavy as one mole of hydrogen atoms simply because each individual ${\text{H}}_{2}$ molecule is twice as heavy than each individual $\text{H}$ atom.

So, one mole of hydrogen atoms has a mass of $\text{1.00794 g}$. If one mole of hydrogen molecules must be twice as heavy than one mole of hydrogen atoms, then the mass of one mole of ${\text{H}}_{2}$ must be

$2 \times \text{1.00794 g " = " 2.01588 g}$