Urea contains what percentage of nitrogen approximately?
A. 35%
B. 46%
C. 15%
D. 21%
Answer: Option B
Solution (By JKSSB Mock Tests)
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:
Ideal gas assumptions: particles have negligible volume, no intermolecular forces, and elastic collisions. Real gases deviate due to finite molecular size and attractions. At high pressure and low temperature, real gases deviate significantly; van der Waals equation corrects. So having strong attractive forces is not an ideal gas property. Ideal gas law PV = nRT is a limiting law.
Explanation:
Naphthalene sublimes on heating, directly changing to vapor, while sand remains. The naphthalene vapor can be condensed on a cold surface. This technique works for any mixture where one component sublimes (naphthalene, camphor, NH₄Cl). Filtration works for insoluble solids in liquids. Magnetic separation for magnetic ores. Distillation for liquid mixtures.
Explanation:
Biological Oxygen Demand (BOD) measures the amount of dissolved oxygen needed by aerobic organisms to break down organic material in water. Clean, unpolluted water has a low BOD, typically less than 5 ppm. Highly polluted water can have a BOD of 17 ppm or much higher, indicating severe organic contamination.
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