The pH of a sample of rain water is found to be 5.6. It is: MCQ with Answer and Explanation

Explanation:
Sulphuric acid (H₂SO₄) is historically called oil of vitriol because it was prepared by distilling green vitriol (ferrous sulfate heptahydrate). It is a dense, oily liquid. Nitric acid is aqua fortis, hydrochloric acid was called muriatic acid or spirit of salt. Sulphuric acid is the king of chemicals due to its widespread use in industries like fertilizer, petroleum refining, and chemical synthesis.

Explanation:
Zinc is more reactive than iron (above in the reactivity series), so it can displace iron: Zn + FeSO₄ → ZnSO₄ + Fe. Silver, copper, and mercury are less reactive than iron and cannot displace it. The reactivity series predicts displacement: a more reactive metal displaces a less reactive one.

Explanation:
Isobars are atoms of different elements with the same mass number but different atomic numbers. ⁴⁰Ar (atomic number 18) and ⁴⁰Ca (atomic number 20) both have mass number 40. Options A and D are isotopes (same element, different mass number). Option C are isotopes of hydrogen. Isobars have different chemical properties because of different proton numbers. Example: ¹⁴C and ¹⁴N.