Final answer:
To determine the mass of 0.40 mole of NaBH4, calculate the molar mass of NaBH4 and multiply by the number of moles, resulting in 15.136 grams.
Step-by-step explanation:
To find out how many grams are in 0.40 mole of NaBH4, we need to first calculate the molar mass of NaBH4. This involves adding the atomic masses of sodium (Na), boron (B), and hydrogen (H). The atomic masses are 22.99 g/mol for Na, 10.81 g/mol for B, and 1.01 g/mol for each of the four hydrogen atoms, giving us:
Molar mass of NaBH4 = 22.99 + 10.81 + (4 × 1.01) = 37.84 g/mol.
Now we can calculate the mass by multiplying the number of moles by the molar mass:
Mass = 0.40 moles × 37.84 g/mol = 15.136 grams of NaBH4.