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Reviewed CSCA Chemistry question · Standard

What is the total number of atoms in 0.150 mol of potassium permanganate, KMnO4? (Avogadro constant = 6.02 × 10^23 mol^-1)

  1. 5.43 × 10^23
  2. 9.03 × 10^22
  3. 1.20 × 10^24
  4. 3.61 × 10^23
Show the answer and explanation

Correct answer

A. 5.43 × 10^23

Principle or equation

Each formula unit of KMnO4 contains 6 atoms (1 K + 1 Mn + 4 O). The total number of atoms = amount of substance (mol) × number of atoms per formula unit × Avogadro constant.

Why this answer is correct

Number of atoms = 0.150 mol × 6 atoms/formula unit × 6.02 × 10^23 mol^-1 = 5.418 × 10^23 ≈ 5.43 × 10^23.

Example

For 0.200 mol of CaCl2 (3 atoms per formula unit), atoms = 0.200 × 3 × 6.02 × 10^23 = 3.61 × 10^23.

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