Input interpretation
![chrome potash alum | relative molecular mass](../image_source/6d946beb60721a6cca5bf51d2f5ed0cc.png)
chrome potash alum | relative molecular mass
Result
![Find the relative molecular mass, M_r, for chrome potash alum: 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: CrKO_8S_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Cr (chromium) | 1 K (potassium) | 1 O (oxygen) | 8 S (sulfur) | 2 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 Cr (chromium) | 1 | 51.9961 K (potassium) | 1 | 39.0983 O (oxygen) | 8 | 15.999 S (sulfur) | 2 | 32.06 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 Cr (chromium) | 1 | 51.9961 | 1 × 51.9961 = 51.9961 K (potassium) | 1 | 39.0983 | 1 × 39.0983 = 39.0983 O (oxygen) | 8 | 15.999 | 8 × 15.999 = 127.992 S (sulfur) | 2 | 32.06 | 2 × 32.06 = 64.12 M_r = 51.9961 + 39.0983 + 127.992 + 64.12 = 283.21](../image_source/ad6b98f1839ab47abd070e6fee525979.png)
Find the relative molecular mass, M_r, for chrome potash alum: 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: CrKO_8S_2 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i Cr (chromium) | 1 K (potassium) | 1 O (oxygen) | 8 S (sulfur) | 2 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 Cr (chromium) | 1 | 51.9961 K (potassium) | 1 | 39.0983 O (oxygen) | 8 | 15.999 S (sulfur) | 2 | 32.06 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 Cr (chromium) | 1 | 51.9961 | 1 × 51.9961 = 51.9961 K (potassium) | 1 | 39.0983 | 1 × 39.0983 = 39.0983 O (oxygen) | 8 | 15.999 | 8 × 15.999 = 127.992 S (sulfur) | 2 | 32.06 | 2 × 32.06 = 64.12 M_r = 51.9961 + 39.0983 + 127.992 + 64.12 = 283.21
Comparisons
![≈ 0.39 × relative molecular mass of fullerene ( ≈ 721 )](../image_source/9806ce57e05ef0ea4d7afff027f08d0e.png)
≈ 0.39 × relative molecular mass of fullerene ( ≈ 721 )
![≈ 1.5 × relative molecular mass of caffeine ( ≈ 194 )](../image_source/20b69d188c0e6d78525144015e3c84a8.png)
≈ 1.5 × relative molecular mass of caffeine ( ≈ 194 )
![≈ 4.8 × relative molecular mass of sodium chloride ( ≈ 58 )](../image_source/4b950af3de06965d34946455a5570720.png)
≈ 4.8 × relative molecular mass of sodium chloride ( ≈ 58 )
Corresponding quantities
![Molar mass M from M = M_uM_r: | 283 g/mol (grams per mole)](../image_source/7ef4dcbacd4ae1586e0ec644182ffff1.png)
Molar mass M from M = M_uM_r: | 283 g/mol (grams per mole)
![Molecular mass m from m = M_rM_u/N_A: | 4.7×10^-22 grams | 4.7×10^-25 kg (kilograms)](../image_source/a468365318a7722a886f3e35eb08dd8c.png)
Molecular mass m from m = M_rM_u/N_A: | 4.7×10^-22 grams | 4.7×10^-25 kg (kilograms)