Isobars are atoms of different elements with the same mass number but different atomic numbers. Argon (Z=18) and Calcium (Z=20) both have a mass number of 40, making them isobars. Options A, B, and D are isotopes, as they represent the same element with different mass numbers.
Explanation:
Froth flotation is used to concentrate sulfide ores. Galena (PbS) is a sulfide ore; it is wetted by oil (pine oil) and comes to the surface with froth, while gangue particles wetted by water settle down. Bauxite (Al₂O₃·2H₂O) is an oxide ore concentrated by leaching (Bayer's process). Magnetite (Fe₃O₄) is magnetic ore separated by magnetic separation. Carnallite (KCl·MgCl₂·6H₂O) is a halide ore.
Explanation:
Crystallization separates a pure solid from a solution by cooling or evaporating the solvent. Impurities remain in the mother liquor. Example: purifying copper sulfate. Distillation for liquids; filtration for insoluble solids.
Explanation:
The universal gas constant R has different values depending on the units used. In SI units (Joules), R = 8.314 J/(mol·K). In L·atm, it is 0.0821 L·atm/(mol·K). Option D mixes SI and L·atm units incorrectly. The value of R is fundamental in thermodynamic calculations.
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