Here's how to calculate the number of moles in 42.5 grams of sodium chloride (NaCl):

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 g/mol + 35.45 g/mol = 58.44 g/mol

2. Use the formula:

* moles = mass / molar mass

3. Plug in the values:

* moles = 42.5 g / 58.44 g/mol

* moles ≈ 0.727 mol

Therefore, there are approximately 0.727 moles in 42.5 grams of sodium chloride.