Question

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?

Answer 1

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.