What is the total number of atoms in 0.500 mol of calcium nitrate, Ca(NO3)2? (Avogadro constant = 6.02 × 10^23 mol^-1)
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Correct answer
C. 2.71 × 10^24 atoms
Principle or equation
One formula unit of Ca(NO3)2 contains 1 Ca + 2 N + 6 O = 9 atoms. Multiply moles by Avogadro's number and by 9.
Why this answer is correct
Moles of formula units = 0.500 mol. Number of formula units = 0.500 × 6.02 × 10^23 = 3.01 × 10^23. Each formula unit has 9 atoms, so total atoms = 3.01 × 10^23 × 9 = 2.71 × 10^24.
Example
For 0.200 mol of H2SO4 (7 atoms per molecule), total atoms = 0.200 × 6.02 × 10^23 × 7 = 8.43 × 10^23.
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