Which bacterium is used as a biofertilizer for fixing atmospheric nitrogen in non-leguminous crops? MCQ with Answer and Explanation

Explanation:
Isotopes are atoms of the same element with the same atomic number (protons) but different mass numbers due to varying number of neutrons. For example, protium (¹H) has 0 neutrons, deuterium (²H) has 1, tritium (³H) has 2. Chemical properties are nearly identical because electronic configuration is the same, but physical properties (mass, density) differ.

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:
Using Boyle's law: P₁V₁ = P₂V₂ => 2 atm × 5 L = 1 atm × V₂ => V₂ = 10 L. As pressure decreases, volume increases. The same mass of gas expands. This is a direct application of inverse proportionality. If temperature and amount of gas are constant, doubling pressure halves volume, etc.