Input interpretation
rubidium dihydrogenarsenate | molar mass
Result
Find the molar mass, M, for rubidium dihydrogenarsenate: 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: RbH_2AsO_4 Use the chemical formula, RbH_2AsO_4, to count the number of atoms, N_i, for each element: | N_i As (arsenic) | 1 H (hydrogen) | 2 O (oxygen) | 4 Rb (rubidium) | 1 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) As (arsenic) | 1 | 74.921595 H (hydrogen) | 2 | 1.008 O (oxygen) | 4 | 15.999 Rb (rubidium) | 1 | 85.4678 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) As (arsenic) | 1 | 74.921595 | 1 × 74.921595 = 74.921595 H (hydrogen) | 2 | 1.008 | 2 × 1.008 = 2.016 O (oxygen) | 4 | 15.999 | 4 × 15.999 = 63.996 Rb (rubidium) | 1 | 85.4678 | 1 × 85.4678 = 85.4678 M = 74.921595 g/mol + 2.016 g/mol + 63.996 g/mol + 85.4678 g/mol = 226.401 g/mol
Unit conversion
0.2264 kg/mol (kilograms per mole)
Comparisons
≈ 0.31 × molar mass of fullerene ( ≈ 721 g/mol )
≈ 1.2 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 3.9 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 3.8×10^-22 grams | 3.8×10^-25 kg (kilograms) | 226 u (unified atomic mass units) | 226 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 226