Keshu

1. General Behavior of Metals with Dilute Acids

• When a metal reacts with a dilute acid, it usually produces:

  • A salt (depending on the acid)

  • Hydrogen gas (H₂)

• General equation: Metal + Acid → Metal Salt + Hydrogen gas.

2. Why These Reactions Occur

• Metals that are more reactive than hydrogen in the reactivity series can push hydrogen out of the acid.

• This is known as a displacement reaction.

• The reaction often releases energy, making the container warm.

3. Factors Affecting the Reaction

• Position in reactivity series:

  • Higher → faster reaction

  • Lower → slower or no reaction

• Surface area:

  • Powdered metal reacts faster than a lump.

• Concentration of acid:

  • More concentrated → faster reaction.

• Temperature:

  • Higher temperature → increased reaction rate.

4. Examples of Metal–Acid Reactions

4.1 Magnesium (very reactive)

• Reaction: Mg + 2HCl → MgCl₂ + H₂

• Observations:

  • Very fast bubbling

  • Heat released

  • Magnesium disappears quickly

4.2 Zinc (moderately reactive)

• Reaction:Zn + H₂SO₄ → ZnSO₄ + H₂

• Observations:

  • Steady stream of bubbles

  • Reaction is neither too slow nor too fast

4.3 Iron (less reactive)

• Reaction:Fe + 2HCl → FeCl₂ + H₂

• Observations:

  • Slow fizzing

  • Iron takes longer to dissolve

  • Slight warming of the solution

5. Metals That Do NOT React with Dilute Acids

These metals are below hydrogen in the reactivity series:

• Copper (Cu)

• Silver (Ag)

• Gold (Au)

• Platinum (Pt)

Reason:They are too unreactive to displace hydrogen from acids.

6. Identifying Hydrogen Gas

You can test for hydrogen using:

• “Pop test”: Bring a burning splint near the gas → it makes a small pop sound.

7. Safety Notes

• Hydrogen is flammable → avoid open flames near reaction.

• Use dilute acids to avoid dangerous heat or rapid reactions.

• Wear goggles and gloves in a laboratory.