Input interpretation
magnesium hydroxide | molar mass
Result
Find the molar mass, M, for magnesium hydroxide: 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: Mg(OH)_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i H (hydrogen) | 2 Mg (magnesium) | 1 O (oxygen) | 2 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) H (hydrogen) | 2 | 1.008 Mg (magnesium) | 1 | 24.305 O (oxygen) | 2 | 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) H (hydrogen) | 2 | 1.008 | 2 × 1.008 = 2.016 Mg (magnesium) | 1 | 24.305 | 1 × 24.305 = 24.305 O (oxygen) | 2 | 15.999 | 2 × 15.999 = 31.998 M = 2.016 g/mol + 24.305 g/mol + 31.998 g/mol = 58.319 g/mol
Unit conversion
0.058319 kg/mol (kilograms per mole)
Comparisons
≈ ( 0.081 ≈ 1/12 ) × molar mass of fullerene ( ≈ 721 g/mol )
≈ 0.3 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 0.998 × molar mass of sodium chloride ( 58.443 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 9.7×10^-23 grams | 9.7×10^-26 kg (kilograms) | 58 u (unified atomic mass units) | 58 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 58