Hydrochloric acid is present in: MCQ with Answer and Explanation

Explanation:
Liquefied Petroleum Gas (LPG) primarily consists of butane (C₄H₁₀) and isobutane, with some propane. For domestic use, it is often a mix of butane and propane. Methane is the main component of CNG and natural gas, which require different storage pressures and infrastructure.

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.

Explanation:
In an electrochemical cell, reduction (gain of electrons) always occurs at the cathode, regardless of whether the cell is electrolytic or galvanic. At the anode, oxidation (loss of electrons) occurs. Memory aid: 'RED CAT' (REDuction at CAThode), 'AN OX' (OXidation at ANode). In electrolysis, the cathode is connected to the negative terminal of the battery, attracting cations which get reduced.