Input interpretation
thallous nitrate | relative molecular mass
Result
Find the relative molecular mass, M_r, for thallous nitrate: 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: TlNO_3 Use the chemical formula, TlNO_3, to count the number of atoms, N_i, for each element: | N_i N (nitrogen) | 1 O (oxygen) | 3 Tl (thallium) | 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 N (nitrogen) | 1 | 14.007 O (oxygen) | 3 | 15.999 Tl (thallium) | 1 | 204.38 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 N (nitrogen) | 1 | 14.007 | 1 × 14.007 = 14.007 O (oxygen) | 3 | 15.999 | 3 × 15.999 = 47.997 Tl (thallium) | 1 | 204.38 | 1 × 204.38 = 204.38 M_r = 14.007 + 47.997 + 204.38 = 266.38
Comparisons
≈ 0.37 × relative molecular mass of fullerene ( ≈ 721 )
≈ 1.4 × relative molecular mass of caffeine ( ≈ 194 )
≈ 4.6 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
Molar mass M from M = M_uM_r: | 266 g/mol (grams per mole)
Molecular mass m from m = M_rM_u/N_A: | 4.4×10^-22 grams | 4.4×10^-25 kg (kilograms)