The separation technique used to obtain different fractions from petroleum is: MCQ with Answer and Explanation

Explanation:
Copper is below hydrogen in the reactivity series, so it cannot displace hydrogen from dilute acids (non-oxidizing acids like HCl or H₂SO₄). Magnesium, zinc, and iron are above hydrogen and react to produce H₂ gas. However, copper reacts with oxidizing acids like HNO₃ and hot conc. H₂SO₄, but not to produce H₂—they produce NO₂/SO₂.

Explanation:
Mendeleev named the missing element eka-aluminium. When gallium was discovered (1875), its properties (density, oxide formula) closely matched Mendeleev's predictions, validating his table. Germanium was eka-silicon; scandium was eka-boron. These predictions were a triumph of the periodic law. Gallium has a low melting point (~30°C) and is used in semiconductors. Mendeleev corrected atomic masses based on group properties.

Explanation:
Rutherford bombarded a thin gold foil with alpha particles. Most passed through, but some were deflected, leading to the nuclear model.