Plaster of Paris is calcium sulfate hemihydrate, CaSO₄·½H₂O. It is obtained by heating gypsum (CaSO₄·2H₂O) at 373 K. It sets to a hard mass on mixing with water reforming gypsum. Option B (2CaSO₄·H₂O) is equivalent to CaSO₄·½H₂O but the conventional representation is CaSO₄·½H₂O. Option A is gypsum, D is anhydrous calcium sulfate. POP is used for making casts, statues, and as a building material.
Explanation:
Bohr's model successfully explains the spectrum of hydrogen and hydrogen-like species (single electron systems like He⁺, Li²⁺). However, it fails to explain the spectra of multi-electron atoms due to electron-electron repulsions and cannot account for the splitting of spectral lines in magnetic (Zeeman) and electric (Stark) fields.
Explanation:
Manganese is extracted by the aluminothermic process (Goldschmidt thermite process) where Mn₃O₄ is reduced by aluminium: 3Mn₃O₄ + 8Al → 9Mn + 4Al₂O₃. This works for metals with less reactivity than Al but not too reactive. Sodium is extracted by electrolysis. Iron is extracted by smelting with coke. Zinc by carbon reduction/electrolysis.
Explanation:
The Wurtz reaction involves the reaction of an alkyl halide with sodium metal in dry ether to form a higher alkane. For example, two molecules of methyl chloride react with two sodium atoms to form ethane (C2H6) and sodium chloride. It is primarily used to synthesize symmetrical alkanes with an even number of carbon atoms.
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