When metals react with acids, they usually form a salt and release hydrogen gas, often with fizzing or bubbling you can see in the test tube.

What Happens When Metals React with Acids?

The basic idea (Quick Scoop)

  • Most metals + dilute acid → salt solution + hydrogen gas.
  • You see:
    • Metal gradually dissolving.
    • Bubbles of gas (this gas is hydrogen).
  • Example:
    • Magnesium + hydrochloric acid → magnesium chloride + hydrogen.

Word equation:
metal + acid → salt + hydrogen.

A simple example

Imagine dropping a strip of zinc into dilute hydrochloric acid:

  • Zinc slowly gets smaller as it reacts.
  • Fizzing (effervescence) starts as hydrogen gas forms.
  • The liquid now contains zinc chloride, a salt.

Symbol equation (one typical example):
\ce{Zn_{(s)}+2HCl_{(aq)}->ZnCl2_{(aq)}+H2_{(g)}}

Another example:
\ce{Mg_{(s)}+2HCl_{(aq)}->MgCl2_{(aq)}+H2_{(g)}}

What products are formed?

  • Salt :
    • Metal part of the salt comes from the metal (Mg, Zn, Ca etc.).
* Acid part of the salt comes from the acid (chloride from HCl, sulfate from H₂SO₄, nitrate from HNO₃).
  • Hydrogen gas (H₂) :
    • Appears as bubbles.
* Can be tested by a lighted splint: hydrogen gives a characteristic ‘pop’ sound.

Some examples (metal + acid → salt + hydrogen):

[5] [3][5] [5]
Metal Acid Salt formed Word equation
Magnesium Hydrochloric acid Magnesium chloride Magnesium + hydrochloric acid → magnesium chloride + hydrogen
Zinc Sulfuric acid Zinc sulfate Zinc + sulfuric acid → zinc sulfate + hydrogen
Calcium Hydrochloric acid Calcium chloride Calcium + hydrochloric acid → calcium chloride + hydrogen

Why does the reaction happen?

Chemically, this is a redox / displacement reaction:

  • The metal atom loses electrons and becomes metal ions in solution (it is oxidized).
  • Hydrogen ions (H⁺) from the acid gain those electrons and join to form hydrogen gas, H₂ (they are reduced).

In simple half‑equations (for a metal M with charge 2+ as an example):

  • Metal: \ce{M->M^{2+}+2e^-}
  • Hydrogen: \ce{2H^++2e^-->H2}

Overall, the metal displaces hydrogen from the acid.

Do all metals react with acids?

No, this depends on the reactivity series.

  • Metals above hydrogen in the reactivity series (like magnesium, zinc, iron) generally react with dilute acids to give salt + hydrogen.
  • Metals below hydrogen (such as copper, silver, gold) do not react with dilute acids under normal conditions, or they react extremely slowly.
* Example: Copper placed in dilute hydrochloric acid shows no visible hydrogen gas in a typical classroom demo.

Very reactive metals (like sodium or potassium) can react too violently with acids, which is why they are not normally used in school labs.

A note on different acids

For common school acids:

  • Hydrochloric acid (HCl) → chloride salts.
  • Sulfuric acid (H₂SO₄) → sulfate salts.
  • Nitric acid (HNO₃) often behaves differently because it is a strong oxidizing agent; it may not release hydrogen gas in the usual way, especially when concentrated.

Quick classroom-style summary (MASH trick)

Many school resources use the acronym MASH :

  • M etal
  • A cid
  • S alt
  • H ydrogen

So, when you’re asked “what happens when metals react with acids?” you can say:

Metals react with dilute acids to form a salt and hydrogen gas, provided the metal is reactive enough (above hydrogen in the reactivity series).

TL;DR:
Put a reactive metal into a dilute acid and you’ll see fizzing as hydrogen gas is released, while the metal gradually dissolves to form a salt in solution.

Information gathered from public forums or data available on the internet and portrayed here.