The atomic number of an element is determined by the number of: MCQ with Answer and Explanation

Explanation:
Bakelite, the first fully synthetic plastic, is a thermosetting phenol formaldehyde resin. It is formed by a condensation reaction between phenol and formaldehyde. Once molded and heated, it sets permanently and cannot be remelted. It is used for electrical switches, utensil handles, and jewelry.

Explanation:
Evaporation of water is a physical change—liquid water changes to water vapor, but the chemical composition (H₂O) remains unchanged. Souring of milk and curd formation involve lactic acid bacteria converting lactose to lactic acid (chemical change). Fermentation of grapes involves yeast converting sugars to ethanol and CO₂. Chemical changes produce new substances. Physical changes only alter the state or form.

Explanation:
CO has a triple bond: one sigma and two pi bonds, with a coordinate covalent character where oxygen donates a lone pair to carbon, forming a bond similar to triple bond. Total shared electrons = 6 (three pairs). Lewis structure shows :C≡O: with formal charges. The bond order is 3. It is isoelectronic with N₂ and CN⁻.