Question

Calculate the mass (in ng) of 2.33 x 1020 atoms of oxygen.

a) 4.69 x 10⁷ ng
b) 6.19 x 10⁶ ng
c) 1.62 x 10⁷ ng
d) 3.73 x 10⁶ ng
e) 2.25 x 10³ ng

Answer 1

The mass of 2.33 x 10^20 atoms of oxygen is calculated by first determining the number of moles and then converting it to a mass, resulting in 6.19 x 10^6 nanograms.

Step-by-step explanation:

To calculate the mass of 2.33 x 1020 atoms of oxygen, we'll start by determining the molar mass of oxygen, which is approximately 16 grams per mole. Next, we'll use Avogadro's number (6.022 x 1023 atoms per mole) to find out the number of moles represented by the given number of oxygen atoms.

Number of moles = 2.33 x 1020 atoms / 6.022 x 1023 atoms/mol = 3.868 x 10-4 mol

Now, to get the mass in grams, we'll multiply the number of moles by the molar mass of oxygen.

Mass in grams = 3.868 x 10-4 mol x 16 g/mol = 0.006189 g

Finally, to convert the mass to nanograms, we'll multiply by 109 ng/g (since there are 1 billion nanograms in a gram).

Mass in nanograms = 0.006189 g x 109 ng/g = 6.189 x 106 ng

Thus, the mass of 2.33 x 1020 atoms of oxygen is 6.19 x 106 ng, which corresponds to option b.