You're asking for the mass of 3.40 moles of sodium chloride (NaCl), not 3.40 grams. Here's how to calculate that:

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. Calculate the mass:

* Multiply the number of moles by the molar mass: 3.40 mol * 58.44 g/mol = 198.7 g

Therefore, there are 198.7 grams in 3.40 moles of sodium chloride (NaCl).