Question

Which one of the following is a chromophore.
A.$-N=N-$
B.$-OH$
C.$-S{O}_{3}H$
D.$-N{H}_2$

Answer 1

Hint: As we know that chromophore is usually a group of atoms that are having electron-withdrawing nature, possess unsaturation, and when present in conjugation imparts color to the compound by absorption of visible light.

Complete answer:
When light falls on a compound, it gets absorbed and results in three types of excitations in the molecule, namely electronic, vibrational, and rotational. The compounds undergo electronic excitation in the UV visible region. In the case of multiple bonded compounds, the $\pi -$ electrons are responsible for absorption and electronic excitation. The colored properties associated with the organic compounds are due to the presence of few groups of atoms known as chromophores which absorb visible light photons.
In Greek, chroma means color, and phoron means bearer. A chromophore is usually a group of atoms that are having electron-withdrawing nature, possess unsaturation, and when present in conjugation imparts color to the compound by absorption of visible light. The chromophores present in ink break down on coming in contact with nitrogen because nitrogen oxidizes them into a substance that does not absorb light in the visible spectrum, or it can be said that absorbs light in the range of wavelength not visible to our eyes.
Therefore, correct answer is option A i.e. $-N=N-.$

Note:
Remember that the chromophore is a color imparting chemical present in a substance. It is to be noted that chlorine can act as a bleaching agent only in the presence of moisture or water. Other than chlorine, some other chemical substances are also used as bleaching agents, such as sulfur dioxide and hydrogen peroxide.