What is the total number of hydrogen atoms in 0.200 mol of ammonium phosphate, (NH4)3PO4? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
A. 1.45 × 10^24
Principle or equation
One formula unit of (NH4)3PO4 contains 3 ammonium ions, each with 4 hydrogen atoms, so 12 hydrogen atoms per formula unit. Use Avogadro's number to convert moles to number of atoms.
Why this answer is correct
Moles of H atoms = 0.200 mol × 12 = 2.40 mol. Number of H atoms = 2.40 mol × 6.02 × 10^23 mol^-1 = 1.4448 × 10^24 ≈ 1.45 × 10^24.
Example
For 0.100 mol (NH4)2SO4, H atoms per formula unit = 8, so moles H = 0.800 mol, atoms = 4.82 × 10^23.
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