Which of the following is a primary air pollutant? MCQ with Answer and Explanation

Explanation:
Urea (NH₂CONH₂) has molar mass 60, with 28 g N, percentage = (28/60)×100 ≈ 46.6%. Rounded to 46%. It is the most concentrated solid nitrogen fertilizer. Ammonium nitrate is 33%, ammonium sulfate 21%.

Explanation:
Sodium chloride is an ionic compound. In the solid state, its Na+ and Cl- ions are held tightly in a crystal lattice and cannot move, so it doesn't conduct. When melted, the lattice breaks down, and the ions become mobile. These free-moving ions carry the electric current, making it a good conductor.

Explanation:
Nitric acid (HNO3) is historically known as Aqua Fortis, which translates to 'strong water' in Latin. This name was given by early alchemists due to its ability to dissolve almost all metals, including silver, which was not dissolved by other known acids at the time.