Input interpretation
terbium(III) sulfate octahydrate | molar mass
Result
Find the molar mass, M, for terbium(III) sulfate octahydrate: 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: Tb_2(SO_4)_3·8H_2O Use the chemical formula to count the number of atoms, N_i, for each element: | N_i H (hydrogen) | 16 O (oxygen) | 20 S (sulfur) | 3 Tb (terbium) | 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) | 16 | 1.008 O (oxygen) | 20 | 15.999 S (sulfur) | 3 | 32.06 Tb (terbium) | 2 | 158.92535 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) | 16 | 1.008 | 16 × 1.008 = 16.128 O (oxygen) | 20 | 15.999 | 20 × 15.999 = 319.980 S (sulfur) | 3 | 32.06 | 3 × 32.06 = 96.18 Tb (terbium) | 2 | 158.92535 | 2 × 158.92535 = 317.85070 M = 16.128 g/mol + 319.980 g/mol + 96.18 g/mol + 317.85070 g/mol = 750.14 g/mol
Unit conversion
0.7501 kg/mol (kilograms per mole)
Comparisons
≈ molar mass of fullerene ( ≈ 721 g/mol )
≈ 3.9 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 13 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 1.2×10^-21 grams | 1.2×10^-24 kg (kilograms) | 750 u (unified atomic mass units) | 750 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 750