Molecule Chemistry Example 5

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Example 5

hard
A molecule of aspirin has the formula C9H8O4\text{C}_9\text{H}_8\text{O}_4. Calculate the total number of atoms in one molecule, the molar mass, and the number of hydrogen atoms in 0.500.50 mol of aspirin.

Solution

  1. 1
    Total atoms per molecule: 9+8+4=219 + 8 + 4 = 21 atoms.
  2. 2
    Molar mass: 9(12.01)+8(1.008)+4(16.00)=108.09+8.064+64.00=180.15 g/mol9(12.01) + 8(1.008) + 4(16.00) = 108.09 + 8.064 + 64.00 = 180.15\,\text{g/mol}.
  3. 3
    H atoms in 0.500.50 mol: each molecule has 8 H atoms, so total =8×0.50×6.022×1023=2.41×1024= 8 \times 0.50 \times 6.022 \times 10^{23} = 2.41 \times 10^{24} hydrogen atoms.

Answer

21 atoms,  M=180.15 g/mol,  2.41×1024 H atoms21\text{ atoms},\; M = 180.15\,\text{g/mol},\; 2.41 \times 10^{24}\text{ H atoms}
Molecular formulas provide all the information needed to calculate molar mass and count specific atoms. Aspirin happens to have the same molar mass as glucose (C6H12O6\text{C}_6\text{H}_{12}\text{O}_6) despite having a completely different formula.

About Molecule

The smallest unit of a covalent substance, consisting of two or more atoms held together by chemical bonds (typically covalent), acting as a single distinct.

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