# What is an example of a diagnostic test that can be done to distinguish between strong acids and weak acids?

Jan 3, 2016

Use a light bulb tester to see if the solution is a good conductor of electricity.

#### Explanation:

A strong acid reacts almost completely with water to form ions.

$\underbrace{\text{HCl")_color(red)("strong acid/few molecules") + "H"_2"O" → underbrace("H"_3"O"^+ + "Cl"^(-))_color(red)("many ions}}$

In a weak acid, only a small percentage of the molecules are converted to ions.

$\underbrace{\text{CH"_3"COOH")_color(red)("weak acid/mostly molecules") + "H"_2"O" ⇌ underbrace("CH"_3"COO"^(-) + "H"_3"O"^+)_color(red)("few ions}}$

In an aqueous solution, the ions conduct electricity.

A solution of a strong acid is a good conductor, because it forms many ions in solution.

A solution of a weak acid is a poor conductor of electricity, because it stays mainly as molecules and forms few ions.

We can check the conductivity of the solutions with a conductivity tester.

When the circuit is completed by a solution containing a large number of ions, the light bulb glows brightly.

If the solution contains only a few ions, the light bulb glows strongly,

This video shows the conductivity tester in operation.