Here's how to calculate the mass of 0.40 moles of sodium chloride (NaCl) in grams:

1. Find the molar mass of NaCl:

* Sodium (Na) has a molar mass of 22.99 g/mol.

* Chlorine (Cl) has a molar mass of 35.45 g/mol.

* The molar mass of NaCl is 22.99 + 35.45 = 58.44 g/mol

2. Use the formula:

* Mass (g) = Moles (mol) × Molar mass (g/mol)

3. Calculate:

* Mass = 0.40 mol × 58.44 g/mol = 23.38 g

Therefore, 0.40 moles of sodium chloride is equal to 23.38 grams.