Methane is the first member of the alkane series. Its molecular formula is: MCQ with Answer and Explanation

Explanation:
Bauxite contains SiO₂ (silica) as impurity. In the Bayer's process, powdered bauxite is treated with hot concentrated NaOH solution. Alumina dissolves forming sodium aluminate (NaAlO₂), while silica does not dissolve and is filtered off. Alternatively, silica can be removed by adding lime during refining. The purified alumina is then electrolyzed in cryolite. NaOH selectively dissolves Al₂O₃ due to its amphoteric nature.

Explanation:
Niels Bohr proposed his model in 1913 to overcome the defects of Rutherford's model. He stated that electrons revolve around the nucleus in specific, discrete circular orbits (shells) with fixed energy, and they do not radiate energy while in these orbits, explaining atomic stability.

Explanation:
Catalysts provide an alternative pathway with lower activation energy, increasing reaction rate without being consumed. They do not affect equilibrium constant or thermodynamic parameters (ΔH, ΔS). They can be solid (heterogeneous), liquid, or gas. Enzymes are liquid-phase catalysts. A catalyst does not change the position of equilibrium, only speeds up attainment.