relative molecular mass of 2,3,7,8,12,13,17,18-octaethyl-21H,23 H-porphine cobalt(II)

2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23 H-porphine cobalt(II) | relative molecular mass

Find the relative molecular mass, M_r, for 2, 3, 7, 8, 12, 13, 17, 18-octaethyl-21H, 23 H-porphine cobalt(II): 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: (C_36H_46CoN_4)^2+ Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Co (cobalt) | 1 C (carbon) | 36 N (nitrogen) | 4 H (hydrogen) | 46 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 Co (cobalt) | 1 | 58.933194 C (carbon) | 36 | 12.011 N (nitrogen) | 4 | 14.007 H (hydrogen) | 46 | 1.008 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 Co (cobalt) | 1 | 58.933194 | 1 × 58.933194 = 58.933194 C (carbon) | 36 | 12.011 | 36 × 12.011 = 432.396 N (nitrogen) | 4 | 14.007 | 4 × 14.007 = 56.028 H (hydrogen) | 46 | 1.008 | 46 × 1.008 = 46.368 M_r = 58.933194 + 432.396 + 56.028 + 46.368 = 593.725