Input interpretation
promethium(III) chloride | molar mass
Result
Find the molar mass, M, for promethium(III) chloride: 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: PmCl_3 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Cl (chlorine) | 3 Pm (promethium) | 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) Cl (chlorine) | 3 | 35.45 Pm (promethium) | 1 | 145 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) Cl (chlorine) | 3 | 35.45 | 3 × 35.45 = 106.35 Pm (promethium) | 1 | 145 | 1 × 145 = 145 M = 106.35 g/mol + 145 g/mol = 251 g/mol
Unit conversion
0.251 kg/mol (kilograms per mole)
Comparisons
≈ 0.35 × molar mass of fullerene ( ≈ 721 g/mol )
≈ 1.3 × molar mass of caffeine ( ≈ 194 g/mol )
≈ 4.3 × molar mass of sodium chloride ( ≈ 58 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 4.2×10^-22 grams | 4.2×10^-25 kg (kilograms) | 251 u (unified atomic mass units) | 251 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 251