Which solution below most likely shows a vivid color? potassium chloride nickel chloride hydrogen chloride lithium chloride
The Correct Answer and Explanation is:
Correct Answer: Nickel chloride
Explanation
Among the compounds listed — potassium chloride (KCl), nickel chloride (NiCl₂), hydrogen chloride (HCl), and lithium chloride (LiCl) — the one most likely to show a vivid color is nickel chloride.
This is because nickel chloride contains a transition metal ion (Ni²⁺). Transition metals are well known for forming colored compounds due to the unique way their electrons behave. In particular, the d-electrons in transition metal ions can absorb certain wavelengths of visible light. When these d-electrons are excited to higher energy levels (a process called d–d transitions), they absorb parts of the visible light spectrum. The remaining unabsorbed light is what we see as the compound’s color. Nickel chloride typically appears bright green in its hydrated form (e.g., NiCl₂·6H₂O).
On the other hand, the other three compounds — potassium chloride, lithium chloride, and hydrogen chloride — do not contain transition metals. Potassium (K⁺), lithium (Li⁺), and hydrogen (H⁺) are alkali metals or non-metals whose ions do not have partially filled d-orbitals. As a result, they do not absorb visible light in the same way and are typically colorless or white in solid form and clear in solution.
- Potassium chloride is usually a white crystalline solid.
- Lithium chloride is also a white solid.
- Hydrogen chloride, in its aqueous form (hydrochloric acid), is a colorless solution.
Therefore, nickel chloride stands out for its vivid green color due to its transition metal character, making it the correct answer.
Summary: Only nickel chloride contains a transition metal capable of producing visible color through d-electron transitions, making it the only compound among the four that shows a vivid color.
