Answer:
The balanced equation shows that 1 mole of Mg reacts with 2 moles of HCl to produce 1 mole of H2.
First, we need to find the number of moles of Mg in 12.5 g of Mg:
12.5 g Mg / 24.31 g/mol = 0.514 moles Mg
Next, we can use the mole ratio from the balanced equation to find the number of moles of H2 produced:
0.514 moles Mg x (1 mole H2 / 1 mole Mg) = 0.514 moles H2
Finally, we can convert the number of moles of H2 to grams:
0.514 moles H2 x 2.016 g/mol = 1.036 g H2
Therefore, 1.036 grams of hydrogen is produced from 12.5 g of Mg reacting with hydrochloric acid in this balanced equation.