1. Analyze the Balanced Chemical Equation:

The balanced equation tells us the mole ratio between reactants and products:

* 2 moles of Na react with 2 moles of H₂O to produce 1 mole of H₂

2. Use the Mole Ratio to Find Moles of Na:

Since we want to produce 4.0 moles of H₂, and the mole ratio is 2 moles Na : 1 mole H₂, we can set up a proportion:

* (2 moles Na) / (1 mole H₂) = (x moles Na) / (4.0 moles H₂)

3. Solve for x (moles of Na):

* Cross-multiply: 2 moles Na * 4.0 moles H₂ = 1 mole H₂ * x moles Na

* Simplify: 8 moles Na = x moles Na

Therefore, 8.0 moles of sodium will react with water to produce 4.0 moles of hydrogen.