Input interpretation
terbium(III) oxide | molar mass
Result
Find the molar mass, M, for terbium(III) oxide: 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_2O_3 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i O (oxygen) | 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) O (oxygen) | 3 | 15.999 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) O (oxygen) | 3 | 15.999 | 3 × 15.999 = 47.997 Tb (terbium) | 2 | 158.92535 | 2 × 158.92535 = 317.85070 M = 47.997 g/mol + 317.85070 g/mol = 365.848 g/mol
Unit conversion
0.365848 kg/mol (kilograms per mole)
Comparisons
≈ 0.51 × molar mass of fullerene ( ≈ 721 g/mol )
≈ 1.9 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 6.3 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 6.1×10^-22 grams | 6.1×10^-25 kg (kilograms) | 366 u (unified atomic mass units) | 366 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 366