Input interpretation
silane | molar mass
Result
Find the molar mass, M, for silane: M = sum _iN_im_i 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: SiH_4 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i H (hydrogen) | 4 Si (silicon) | 1 Look up the atomic mass, m_i, in g·mol^(-1) for each element in the periodic table: | N_i | m_i/g·mol^(-1) H (hydrogen) | 4 | 1.008 Si (silicon) | 1 | 28.085 Multiply N_i by m_i to compute the mass for each element. Then sum those values to compute the molar mass, M: Answer: | | | N_i | m_i/g·mol^(-1) | mass/g·mol^(-1) H (hydrogen) | 4 | 1.008 | 4 × 1.008 = 4.032 Si (silicon) | 1 | 28.085 | 1 × 28.085 = 28.085 M = 4.032 g/mol + 28.085 g/mol = 32.117 g/mol
Unit conversion
0.032117 kg/mol (kilograms per mole)
Comparisons
≈ ( 0.17 ≈ 1/6 ) × molar mass of caffeine ( ≈ 194 g/mol )
≈ 0.55 × molar mass of sodium chloride ( ≈ 58 g/mol )
≈ 1.8 × molar mass of water ( ≈ 18 g/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 5.3×10^-23 grams | 5.3×10^-26 kg (kilograms) | 32 u (unified atomic mass units) | 32 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 32