Question 4
18 g of carbon dioxide contains how many oxygen atoms?

4.92×10²³ atoms of oxygen.

Explanation:

We'll begin by calculating the number of mole of oxygen in 1 mole of CO₂. This can be obtained as follow:

1 mole of CO₂ contains 2 mole of oxygen.

1 mole of CO₂ = 12 + (2×16)

= 12 + 32

= 44 g

Thus,

44 g of CO₂ contains 2 moles of oxygen.

Next, we shall determine the number of mole of oxygen in 18 g of CO₂. This can be obtained as follow:

44 g of CO₂ contains 2 moles of oxygen.

Therefore, 18 g of CO₂ will contain

= (18 × 2)/ 44 = 0.818 mole of oxygen.

Finally, we shall determine the number of atoms in 0.818 mole of oxygen. This can be obtained as follow:

From Avogadro's hypothesis,

1 mole = 6.02×10²³ atoms.

Therefore,

0.818 mole = 0.818 × 6.02×10²³ atoms.

0.818 mole of oxygen = 4.92×10²³ atoms.

Thus, 18 g of CO₂ contains 4.92×10²³ atoms of oxygen.