Here's how to calculate the number of moles of chlorine gas (Cl₂):

1. Find the molar mass of chlorine gas (Cl₂):

* The atomic mass of chlorine (Cl) is approximately 35.45 g/mol.

* Since chlorine gas exists as a diatomic molecule (Cl₂), the molar mass is 2 * 35.45 g/mol = 70.90 g/mol.

2. Use the formula:

* moles = mass / molar mass

3. Plug in the values:

* moles = 142 g / 70.90 g/mol

* moles ≈ 2.00 mol

Therefore, 142 grams of chlorine gas is approximately equal to 2.00 moles.