Answer:To find the number of moles of H2 produced by 12.5 moles of H3PO4, we need to use the balanced equation for the reaction.
The balanced equation for the decomposition of H3PO4 is:
H3PO4 -> 3H2 + P4O10
From this equation we see that for every 1 mole of H3PO4, 3 moles of H2 are produced. Therefore, we can use a mole ratio to find the number of moles of H2 produced by 12.5 moles of H3PO4.
12.5 moles of H3PO4 * (3 moles H2 / 1 mole H3PO4) = 37.5 moles of H2