Input interpretation
aspirin | molar mass
Result
Find the molar mass, M, for aspirin: M = sum _iN_im_i Plan: • Write the chemical formula and gather atomic masses from the periodic table. • Determine values for N_i and m_i using these items. • Finally, compute the mass. Write the chemical formula: (CH_3CO_2)C_6H_4CO_2H Use the chemical formula to count the number of atoms, N_i, for each element: | N_i C (carbon) | 9 H (hydrogen) | 8 O (oxygen) | 4 Look up the atomic mass, m_i, in g·mol^(-1) for each element in the periodic table: | N_i | m_i/g·mol^(-1) C (carbon) | 9 | 12.011 H (hydrogen) | 8 | 1.008 O (oxygen) | 4 | 15.999 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molar mass, M: Answer: | | | N_i | m_i/g·mol^(-1) | mass/g·mol^(-1) C (carbon) | 9 | 12.011 | 9 × 12.011 = 108.099 H (hydrogen) | 8 | 1.008 | 8 × 1.008 = 8.064 O (oxygen) | 4 | 15.999 | 4 × 15.999 = 63.996 M = 108.099 g/mol + 8.064 g/mol + 63.996 g/mol = 180.159 g/mol
Unit conversion
0.18016 kg/mol (kilograms per mole)
Comparisons
≈ ( 0.25 ≈ 1/4 ) × molar mass of fullerene ( ≈ 721 g/mol )
≈ 0.93 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 3.1 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 3×10^-22 grams | 3×10^-25 kg (kilograms) | 180 u (unified atomic mass units) | 180 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 180