Input interpretation
sodium arsenite | molar mass
Result
Find the molar mass, M, for sodium arsenite: 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: NaAsO_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i As (arsenic) | 1 Na (sodium) | 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) As (arsenic) | 1 | 74.921595 Na (sodium) | 1 | 22.98976928 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) As (arsenic) | 1 | 74.921595 | 1 × 74.921595 = 74.921595 Na (sodium) | 1 | 22.98976928 | 1 × 22.98976928 = 22.98976928 O (oxygen) | 2 | 15.999 | 2 × 15.999 = 31.998 M = 74.921595 g/mol + 22.98976928 g/mol + 31.998 g/mol = 129.909 g/mol
Unit conversion
0.129909 kg/mol (kilograms per mole)
Comparisons
≈ ( 0.18 ≈ 1/6 ) × molar mass of fullerene ( ≈ 721 g/mol )
≈ 0.67 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 2.2 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 2.2×10^-22 grams | 2.2×10^-25 kg (kilograms) | 130 u (unified atomic mass units) | 130 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 130