You're asking about the reaction between magnesium (Mg) and nitric acid (HNO₃) to produce magnesium nitrate (Mg(NO₃)₂) and hydrogen gas (H₂). Here's how to solve this problem:

1. Balanced Chemical Equation:

The balanced chemical equation for this reaction is:

Mg + 2 HNO₃ → Mg(NO₃)₂ + H₂

2. Mole Ratio:

The balanced equation tells us that 1 mole of magnesium reacts with 2 moles of nitric acid to produce 1 mole of magnesium nitrate.

3. Calculation:

You provided 8 moles of nitric acid. Using the mole ratio from the balanced equation, we can find the moles of magnesium nitrate produced:

* (8 moles HNO₃) * (1 mole Mg(NO₃)₂ / 2 moles HNO₃) = 4 moles Mg(NO₃)₂

Therefore, 4 moles of magnesium nitrate are produced when 8 moles of nitric acid react with magnesium.