Input interpretation
magnesium phosphate hydrate | molar mass
Result
Find the molar mass, M, for magnesium phosphate hydrate: 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_3(PO_4)_2·xH_2O Use the chemical formula to count the number of atoms, N_i, for each element: | N_i H (hydrogen) | 2 Mg (magnesium) | 3 O (oxygen) | 9 P (phosphorus) | 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) | 3 | 24.305 O (oxygen) | 9 | 15.999 P (phosphorus) | 2 | 30.973761998 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) | 3 | 24.305 | 3 × 24.305 = 72.915 O (oxygen) | 9 | 15.999 | 9 × 15.999 = 143.991 P (phosphorus) | 2 | 30.973761998 | 2 × 30.973761998 = 61.947523996 M = 2.016 g/mol + 72.915 g/mol + 143.991 g/mol + 61.947523996 g/mol = 280.870 g/mol
Unit conversion
0.28087 kg/mol (kilograms per mole)
Comparisons
≈ 0.39 × molar mass of fullerene ( ≈ 721 g/mol )
≈ 1.4 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 4.8 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 4.7×10^-22 grams | 4.7×10^-25 kg (kilograms) | 281 u (unified atomic mass units) | 281 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 281