Input interpretation
potassium hexaiodoplatinate(IV) | relative molecular mass
Result
Find the relative molecular mass, M_r, for potassium hexaiodoplatinate(IV): M_r = sum _iN_im_i/m_u 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: K_2PtI_6 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i I (iodine) | 6 K (potassium) | 2 Pt (platinum) | 1 Look up the atomic mass, m_i, in unified atomic mass units, u, for each element in the periodic table. Since m_i is divided by the atomic mass constant, m_u, the result is a unitless relative atomic mass: | N_i | m_i/m_u I (iodine) | 6 | 126.90447 K (potassium) | 2 | 39.0983 Pt (platinum) | 1 | 195.084 Multiply N_i by m_i/m_u to compute the relative mass for each element. Then sum those values to compute the relative molecular mass, M_r: Answer: | | | N_i | m_i/m_u | relative mass I (iodine) | 6 | 126.90447 | 6 × 126.90447 = 761.42682 K (potassium) | 2 | 39.0983 | 2 × 39.0983 = 78.1966 Pt (platinum) | 1 | 195.084 | 1 × 195.084 = 195.084 M_r = 761.42682 + 78.1966 + 195.084 = 1034.707
Comparisons
≈ 1.4 × relative molecular mass of fullerene ( ≈ 721 )
≈ 5.3 × relative molecular mass of caffeine ( ≈ 194 )
≈ 18 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
Molar mass M from M = M_uM_r: | 1 kg/mol (kilogram per mole)
Molecular mass m from m = M_rM_u/N_A: | 1.7×10^-21 grams | 1.7×10^-24 kg (kilograms)