A single hydrogen atom has a mass of 1.67 * 10-24 g. A sodium atom has an atomic mass of 23. How many sodium atoms are required to reach a total mass of 973 mg in a substance of pure sodium?

2.55 * 10²² Na Atoms

Solution:

Data Given:

M. Mass of Na = 23 g. mol⁻¹

Mass of Na = 973 mg = 0.973 g

# of Na Atoms = ?

Step 1: Calculate Moles of Na as:

Moles = Mass : M. Mass

Moles = 0.973 g : 23 g. mol⁻¹

Moles = 0.0423 mol

Step 2: Calculate No, of Na Atoms as:

As 1 mole of sodium atoms counts 6.022 * 10²³ and equals exactly to the mass of 23 g. So, we can write,

Moles = No. of Na Atoms : 6.022 * 10²³ Na Atoms. mol⁻¹

Solving for No. of Na Atoms,

No. of Na Atoms = Moles * 6.022 * 10²³ Na Atoms. mol⁻¹

No. of Na Atoms = 0.0423 mol * 6.022 * 10²³ Na Atoms. mol⁻¹

No. of Na Atoms = 2.55 * 10²² Na Atoms

Conclusion:

2.55 * 10²² sodium atoms are required to reach a total mass of 973 mg in a substance of pure sodium.