1. Balanced Chemical Equation:

The balanced chemical equation for the reaction is:

Mg(s) + 2HCl(aq) → MgCl₂(aq) + H₂(g)

2. Mole Ratio:

From the balanced equation, we see that 2 moles of HCl react to produce 1 mole of H₂.

3. Moles of H₂ produced:

Since we have 3143 moles of HCl, we can calculate the moles of H₂ produced:

* (3143 moles HCl) * (1 mole H₂ / 2 moles HCl) = 1571.5 moles H₂

4. Volume of H₂ at STP:

At Standard Temperature and Pressure (STP), 1 mole of any ideal gas occupies 22.4 L. We can use this to calculate the volume of H₂ produced:

* (1571.5 moles H₂) * (22.4 L/mole) = 35,213.6 L

Therefore, 35,213.6 liters of hydrogen gas are produced from the complete reaction of 3143 moles of hydrochloric acid at STP.