What happens when a naphthalene ball is burnt in a metal plate in open space?

Correct Option: It burns with a yellow flame with black soot deposited on the metal plate.

Explanation:

Naphthalene (${\text{C}}_{10}{\text{H}}_8$) is an aromatic hydrocarbon. Hydrocarbons are classified into saturated and unsaturated compounds. Naphthalene belongs to the class of unsaturated hydrocarbons containing a high carbon-to-hydrogen ratio.

When naphthalene is burnt in open space, the available atmospheric oxygen is insufficient to completely oxidize all the carbon atoms present in its molecule. This leads to incomplete combustion.

During incomplete combustion, unburnt carbon particles (soot) are produced. These carbon particles become incandescent (glow yellow) when heated in the flame, giving the flame a characteristic smoky, luminous yellow appearance.

When a metal plate is held over or under the burning naphthalene, these unburnt carbon particles collide with the cool metallic surface and deposit on it, forming a layer of fine black soot.

Therefore, when a naphthalene ball is burnt on a metal plate in open space, it burns with a yellow flame and black soot is deposited on the metal plate.