Enzyme catalase decomposes hydrogen peroxide in cells. This enzyme is present in: MCQ with Answer and Explanation

Explanation:
Combustion of methane (CH₄ + 2O₂ → CO₂ + 2H₂O + heat) is an exothermic reaction, releasing heat to surroundings. Melting, evaporation, and sublimation are endothermic phase changes requiring heat absorption to overcome intermolecular forces. Exothermic reactions: burning, respiration, neutralization (usually), condensation, freezing. Endothermic: photosynthesis, cooking, melting, boiling.

Explanation:
NH₄Cl is from HCl (strong) and NH₄OH (weak). Its aqueous solution is acidic due to hydrolysis of NH₄⁺. NaCl is neutral (strong-strong). CH₃COONa basic (weak-strong).

Explanation:
Rate of diffusion is inversely proportional to the square root of molar mass (Graham's law). Lighter gases diffuse faster. Molar masses: NH₃ = 17, N₂ = 28, O₂ = 32, CO₂ = 44 g/mol. Therefore NH₃ has the lowest molar mass and diffuses fastest. This law also explains why the smell of perfume spreads quickly. NH₃ is lighter than air and would rise.