Input interpretation
lithium borohydride | molar mass
Result
Find the molar mass, M, for lithium borohydride: 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: LiBH_4 Use the chemical formula to count the number of atoms, N_i, for each element: | N_i B (boron) | 1 H (hydrogen) | 4 Li (lithium) | 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) B (boron) | 1 | 10.81 H (hydrogen) | 4 | 1.008 Li (lithium) | 1 | 6.94 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) B (boron) | 1 | 10.81 | 1 × 10.81 = 10.81 H (hydrogen) | 4 | 1.008 | 4 × 1.008 = 4.032 Li (lithium) | 1 | 6.94 | 1 × 6.94 = 6.94 M = 10.81 g/mol + 4.032 g/mol + 6.94 g/mol = 21.78 g/mol
Unit conversion
0.0218 kg/mol (kilograms per mole)
Comparisons
≈ 0.37 × molar mass of sodium chloride ( ≈ 58 g/mol )
≈ 1.2 × molar mass of water ( ≈ 18 g/mol )
≈ 1.8 × carbon-12 molar mass ( ≈ 0.012 kg/mol )
Corresponding quantities
Mass of a molecule m from m = M/N_A: | 3.6×10^-23 grams | 3.6×10^-26 kg (kilograms) | 22 u (unified atomic mass units) | 22 Da (daltons)
Relative molecular mass M_r from M_r = M_u/M: | 22