Question

30 points

Which example has 1.2×10^24 hydrogen atoms?

1 mole of water (H2O)
1 mole of methane (CH4)
2 moles of ammonia (NH3)
2 moles of hydrogen gas (H2)

Answer 1

Answer:

1 mole of water (H2O)

Explanation:

Water has a chemical formula of H2O, there will be 2 moles of hydrogen in every mole of water.

In one mole of water, there will exist approximately 6.02×10^23 water molecules.

So, there will be a total of 6.02×10^23×2≈1.2⋅10^24 hydrogen atoms.

Answer 2

Answer:

1 mole of water $(H_{2}O)$

Explanation:

We know that the Avogadro's number is the amount of elemental units in any mole.

The Avogadro's number is $(6.02).10^{23}$

This means that for example, in a mole of atoms of hydrogen there are $(6.02).10^{23}$ atoms of hydrogen.

To find in which example there are $(1.2).10^{24}$ hydrogen atoms we first need to divide this number by the Avogadro's number :

$\frac{(1.2).10^{24}}{(6.02).10^{23}}$ ≅ 2  ⇒

We need to find in which example there are 2 moles of atoms of hydrogen.

In one molecule of $H_{2}O$ there are 2 atoms of hydrogen and 1 atom of oxygen. In terms of moles, in 1 mole of water there are 2 moles of atoms of hydrogen and 1 mole of atoms of oxygen.

The mole of water is the only example in which there are 2 moles of atoms of hydrogen ⇒  The correct option is 1 mole of $(H_{2}O)$