Input interpretation
![mercuric chloride | relative molecular mass](../image_source/6571e51313242a5ab0a2e397cd069196.png)
mercuric chloride | relative molecular mass
Result
![Find the relative molecular mass, M_r, for mercuric chloride: 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: HgCl_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Cl (chlorine) | 2 Hg (mercury) | 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 Cl (chlorine) | 2 | 35.45 Hg (mercury) | 1 | 200.592 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 Cl (chlorine) | 2 | 35.45 | 2 × 35.45 = 70.90 Hg (mercury) | 1 | 200.592 | 1 × 200.592 = 200.592 M_r = 70.90 + 200.592 = 271.49](../image_source/c13f626cea335c3ce72b1cf391649781.png)
Find the relative molecular mass, M_r, for mercuric chloride: 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: HgCl_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Cl (chlorine) | 2 Hg (mercury) | 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 Cl (chlorine) | 2 | 35.45 Hg (mercury) | 1 | 200.592 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 Cl (chlorine) | 2 | 35.45 | 2 × 35.45 = 70.90 Hg (mercury) | 1 | 200.592 | 1 × 200.592 = 200.592 M_r = 70.90 + 200.592 = 271.49
Comparisons
![≈ 0.38 × relative molecular mass of fullerene ( ≈ 721 )](../image_source/fe4cc30245d32fb91ad064204a506cb0.png)
≈ 0.38 × relative molecular mass of fullerene ( ≈ 721 )
![≈ 1.4 × relative molecular mass of caffeine ( ≈ 194 )](../image_source/279c26659990c3d8b96b3fb5b5bde2b6.png)
≈ 1.4 × relative molecular mass of caffeine ( ≈ 194 )
![≈ 4.6 × relative molecular mass of sodium chloride ( ≈ 58 )](../image_source/5d29281b47b2576f183fd233854c0222.png)
≈ 4.6 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
![Molar mass M from M = M_uM_r: | 271 g/mol (grams per mole)](../image_source/e3f46cf3a7bf2ef3fa63cadfc3dba342.png)
Molar mass M from M = M_uM_r: | 271 g/mol (grams per mole)
![Molecular mass m from m = M_rM_u/N_A: | 4.5×10^-22 grams | 4.5×10^-25 kg (kilograms)](../image_source/f411f419a4242034cae57765919ed633.png)
Molecular mass m from m = M_rM_u/N_A: | 4.5×10^-22 grams | 4.5×10^-25 kg (kilograms)