Question

How many moles of hydrogen

Answer 1

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.