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.
Explanation:
Urea is synthesized by reacting ammonia and carbon dioxide under high pressure and temperature: 2NH₃ + CO₂ → NH₂COONH₄ (ammonium carbamate) → (NH₂)₂CO + H₂O. This is the Bosch-Meiser urea process. It is the most concentrated solid nitrogenous fertilizer. Urea is also used in animal feed, plastics, and pharmaceuticals.
Explanation:
J.J. Thomson proposed the 'plum pudding' model (also called watermelon model) where the atom was considered a sphere of positive charge with electrons embedded like seeds. Rutherford's gold foil experiment disproved this by showing a dense, positively charged nucleus. Dalton proposed the indivisible atom theory. Bohr gave the model with discrete energy levels. Thomson discovered the electron but couldn't explain the nucleus.
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