Answer:
1.72 moles of H₂
Explanation:
The balanced equation
2Na+ 2H₂O → 2NaOH + 1C
tells us we'll get 1 mole of H₂ for every 2 moles of NaOH. We can express this as a molar ratio: (1 mole H₂)/(2 moles NaOH).
The reaction produces 138 g of NaOH. Divide this mass by the molar mass of NaOH (39.99 g/mole)to obtain moles NaOH:
138g NaOH/(40 g/mole) = 3.45 moles of NaOH.
To find the moles H₂ produced, we can multiply the moles NaOH by the molar ratio from above:
(3.45 moles NaOH)*((1 mole H₂)/(2 moles NaOH) = (3.45/2) moles H₂. [Note how the "moles NaOH" unit cancels, leaving just "moles H₂"]
We should produce 1.72 moles of H₂.
