The concentration of dissolved oxygen in water is a measure of its:
A. Acidity
B. Biological Oxygen Demand (BOD)
C. Hardness
D. Purity
Answer: Option B
Solution (By JKSSB Mock Tests)
The amount of dissolved oxygen is crucial for aquatic life. The Biological Oxygen Demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material. High BOD indicates high organic pollution and low dissolved oxygen levels.
Explanation:
This is a single displacement reaction. Iron (Fe) is more reactive than Copper (Cu), so it displaces copper from its aqueous sulfate solution. The blue color of CuSO₄ fades, and a brown deposit of Cu forms. Reactivity series dictates that a more reactive metal displaces a less reactive one.
Explanation:
In 1913, Niels Bohr modified Rutherford's model to explain atomic stability and emission spectra. He introduced the concept of quantized electron orbits (or energy levels), stating that electrons revolve in specific, fixed orbits without radiating energy, and they only emit or absorb energy when jumping between these discrete levels.
Explanation:
Ionic (electrovalent) bond involves complete transfer of one or more valence electrons. Example: Na → Na⁺ + e⁻, Cl + e⁻ → Cl⁻, forming NaCl. Covalent bond shares electrons; coordinate bond is a special covalent bond where one atom donates both electrons.
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