A solution with [H⁺] = 10⁻⁹ M has pH: MCQ with Answer and Explanation

Explanation:
Refining is the final step in metallurgy to obtain pure metal. Poling is used for copper to remove oxide impurities. Liquation separates low-melting metals (like tin) from high-melting impurities. Zone refining is used for producing ultra-pure semiconductors (like Si, Ge) based on the principle that impurities are more soluble in the molten state.

Explanation:
Ernest Rutherford, along with his students Geiger and Marsden, conducted the famous gold foil experiment in 1911. By observing that a few alpha particles bounced back, he concluded that the atom has a small, dense, positively charged center called the nucleus.

Explanation:
Ammonium ion (NH₄⁺) is formed when NH₃ donates its lone pair to H⁺, forming a coordinate (dative) bond. CH₄ and H₂O have ordinary covalent bonds; NaCl is ionic. In NH₄⁺, all four N–H bonds become equivalent.