Question

Which gas is evolved when magnesium metal reacts with very dilute HNO₃?

Options

• Oxygen

• Nitrogen

• Hydrogen

• Nitrogen Dioxide

Answer 1

Hydrogen

Explanation:

Very dilute HNO3 acts as a regular (non‑oxidising) acid and reacts with magnesium to form magnesium nitrate and H₂ gas: \[\ce{Mg + 2HNO3 -> Mg(NO3)2 + H2}\]. Concentrated HNO₃, being oxidizing, yields nitrogen oxides instead.