Which of the following metals is preserved in kerosene oil? MCQ with Answer and Explanation

Explanation:
Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from dilute acids (non-oxidizing acids like HCl or H₂SO₄). Magnesium, zinc, and iron are above hydrogen and react to produce H₂ gas. However, copper reacts with oxidizing acids like HNO₃ and hot conc. H₂SO₄, but not to produce H₂—they produce NO₂/SO₂.

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:
Lysozyme is an antibacterial enzyme found in tears, saliva, and egg white. It breaks down bacterial cell walls. Lipase digests fats, trypsin and pepsin digest proteins. Lysozyme is part of the innate immune system.