Input interpretation
creatine-phosphate | relative molecular mass
Result
Find the relative molecular mass, M_r, for creatine-phosphate: 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_4H_10N_3O_5P_1 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i C (carbon) | 4 H (hydrogen) | 12 N (nitrogen) | 3 O (oxygen) | 6 P (phosphorus) | 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 C (carbon) | 4 | 12.011 H (hydrogen) | 12 | 1.008 N (nitrogen) | 3 | 14.007 O (oxygen) | 6 | 15.999 P (phosphorus) | 1 | 30.973761998 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 C (carbon) | 4 | 12.011 | 4 × 12.011 = 48.044 H (hydrogen) | 12 | 1.008 | 12 × 1.008 = 12.096 N (nitrogen) | 3 | 14.007 | 3 × 14.007 = 42.021 O (oxygen) | 6 | 15.999 | 6 × 15.999 = 95.994 P (phosphorus) | 1 | 30.973761998 | 1 × 30.973761998 = 30.973761998 M_r = 48.044 + 12.096 + 42.021 + 95.994 + 30.973761998 = 229.129
Comparisons
≈ 0.32 × relative molecular mass of fullerene ( ≈ 721 )
≈ 1.2 × relative molecular mass of caffeine ( ≈ 194 )
≈ 3.9 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
Molar mass M from M = M_uM_r: | 229 g/mol (grams per mole)
Molecular mass m from m = M_rM_u/N_A: | 3.8×10^-22 grams | 3.8×10^-25 kg (kilograms)