Here's how to calculate the number of moles in 4 grams of sodium carbonate (Na₂CO₃):

1. Find the molar mass of sodium carbonate:

* Na: 22.99 g/mol (and there are 2 sodium atoms)

* C: 12.01 g/mol

* O: 16.00 g/mol (and there are 3 oxygen atoms)

Molar mass of Na₂CO₃ = (2 * 22.99) + 12.01 + (3 * 16.00) = 105.99 g/mol

2. Use the formula:

Moles = Mass / Molar Mass

3. Plug in the values:

Moles = 4 g / 105.99 g/mol

4. Calculate:

Moles ≈ 0.0377 mol

Therefore, there are approximately 0.0377 moles in 4 grams of sodium carbonate.