Rutherford's alpha-scattering experiment led to the discovery of the: MCQ with Answer and Explanation

Explanation:
Sublimation is the direct transition from solid to gas phase. Examples: naphthalene, camphor, iodine, solid CO₂ (dry ice). Evaporation is liquid to gas; condensation is gas to liquid; distillation separates liquid mixtures based on boiling points.

Explanation:
Mendeleev placed Cobalt (atomic mass 58.9) before Nickel (atomic mass 58.7) to maintain chemical similarities, violating his own periodic law based on atomic mass. Isotopes weren't an issue then, and H's position was ambiguous, but the Co/Ni placement is a classic anomaly of his atomic mass-based table.

Explanation:
A positive catalyst increases reaction rate by lowering activation energy. Decreasing temperature generally slows reactions. Decreasing concentration reduces collision frequency, lowering rate. Larger pieces have less surface area, slower reaction. Other rate-increasing factors: increasing temperature, increasing pressure (for gases), using finely powdered solids, and light for photochemical reactions.