Question

A sample of CaCl₂ is placed in the flame of a Bunsen burner. The component of the substance which is responsible for the production of the flame colour is:

1. Ca²⁺
2. Ca
3. Cl^−
4. Cl
Why is the textbook answer Ca and not Ca²⁺?

Answer 1

The color observed in a flame test for CaCl₂ is due to the excitation of electrons in the calcium ions, but the elemental form 'Ca' is often used to describe the source of the color. The correct option is (2).

Step-by-step explanation:

When a sample of CaCl₂ is placed in the flame of a Bunsen burner, it is the calcium ion (Ca) that is responsible for the color observed in the flame, not the Ca²⁺ ion.

In the context of flame tests, it's common to refer to the metal by its elemental form when describing the emitted color, even though in reality it's the ions that are present in the compounds.

The color we see is due to the electron transitions in the metal ion, in this case specifically calcium ions, but for simplicity, textbooks may refer to the element itself (Ca).

This occurs because as the Ca²⁺ ions are heated, their electrons become excited and jump to higher energy levels. When the electrons fall back down to their original energy levels, they release light of a characteristic color.