The fuel with the highest cetane number is: MCQ with Answer and Explanation

Explanation:
Valency is the number of electrons an atom can lose, gain, or share to achieve a stable octet. It determines the number of chemical bonds it can form. For example, carbon has valency 4, oxygen 2, chlorine 1. Atomic number is number of protons, mass number is protons+neutrons, ionization energy is energy required to remove electron.

Explanation:
Polythene (polyethylene) softens on heating and can be remolded, thus thermoplastic. Bakelite and melamine are thermosetting (cannot be remolded). Vulcanized rubber is also thermoset due to cross-linking. Thermoplastics have linear or branched chains, no cross-links.

Explanation:
A solution turning red litmus blue is basic, so pH > 7. Among options, pH 9 is basic. pH 2 and 5 are acidic (blue litmus turns red). pH 7 is neutral. Litmus is a natural indicator extracted from lichens. Red litmus in base remains blue, blue litmus in acid turns red. Practical: Phenolphthalein gives pink in basic solution (pH > 8.3).