1. Write the balanced chemical equation:

The reaction between sodium (Na) and water (H₂O) produces sodium hydroxide (NaOH) and hydrogen gas (H₂):

2 Na + 2 H₂O → 2 NaOH + H₂

2. Determine the mole ratio:

From the balanced equation, we see that 2 moles of sodium react to produce 1 mole of hydrogen gas.

3. Calculate the moles of hydrogen gas:

Using the mole ratio, we can set up a proportion:

(2 moles Na) / (1 mole H₂) = (0.066 moles Na) / (x moles H₂)

Solving for x:

x = (0.066 moles Na) * (1 mole H₂) / (2 moles Na) = 0.033 moles H₂

Therefore, 0.033 moles of hydrogen gas are produced when 0.066 moles of sodium is completely reacted.