A compound gives an orange-red color to non-luminous flame. This compound is likely to contain?

1. Analyze the question

The question asks you to identify a metal cation based on the characteristic color it imparts to a non-luminous Bunsen flame. This is a classic "Flame Test" question frequently tested in JAMB Chemistry.

2. Explain the concept

The Flame Test is an analytical procedure used in chemistry to detect the presence of certain metal ions based on the emission spectrum of the element. When a metal salt is heated in a non-luminous flame, the electrons in the metal atoms absorb energy and become "excited." As they return to their ground state, they release this energy as light of a specific wavelength (color).

Each metal ion produces a unique flame color:

• Sodium (Na⁺): Intense golden-yellow.
• Calcium (Ca²⁺): Brick-red or orange-red.
• Potassium (K⁺): Lilac (pale violet).
• Copper (Cu²⁺): Blue-green.
• Barium (Ba²⁺): Apple-green.

3. Show the solution

• Option A (Na⁺): Sodium ions produce a characteristic golden-yellow flame. This does not match the description.
• Option B (Ca²⁺): Calcium ions are well-known in qualitative analysis for producing a brick-red or orange-red color in a non-luminous flame. This matches the description perfectly.
• Option C (Fe³⁺) and D (Fe²⁺): Iron ions do not produce a distinct flame color that is typically used for identification in the standard flame test; they are usually identified by their reactions with reagents like NaOH or K₄[Fe(CN)₆].

Comparing the options to the known flame test results, the orange-red color is the signature of Calcium (Ca²⁺).

4. Identify the answer

The correct option is B.

5. Tip for your exam

To remember these easily, use this simple mnemonic:

• Na (Sodium) = Na-yellow (Golden-yellow).
• Ca (Calcium) = Ca-brick (Brick-red/Orange-red).
• K (Potassium) = K-lilac (Lilac).

Always remember that the flame must be non-luminous (the blue flame) to get an accurate reading, as a luminous (yellow) flame would mask the color of the metal!