What is the total number of ions in 0.150 mol of sodium sulfate, Na2SO4? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
A. 2.71 × 10^23
Principle or equation
Each formula unit of Na2SO4 dissociates into 2 Na+ ions and 1 SO4^2- ion, giving 3 ions per formula unit. Total ions = moles × Avogadro constant × ions per formula unit.
Why this answer is correct
Moles of Na2SO4 = 0.150 mol. Ions per formula unit = 2 + 1 = 3. Total ions = 0.150 × 6.02 × 10^23 × 3 = 2.709 × 10^23, which rounds to 2.71 × 10^23.
Example
For 0.100 mol of CaCl2, ions per formula unit = 3, total ions = 0.100 × 6.02 × 10^23 × 3 = 1.81 × 10^23.
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