A gas at constant temperature occupies 5 L at 2 atm. What is the volume at 1 atm? MCQ with Answer and Explanation

Explanation:
Ozone decomposes to O₂, leaving no residual taste or toxic by-products like trihalomethanes. However, it must be generated on-site and is more expensive.

Explanation:
Melting of wax is a physical change because it involves only a change in state from solid to liquid without altering the chemical composition. The wax remains the same hydrocarbon mixture. In contrast, rusting of iron (Fe₂O₃·xH₂O formation), burning of magnesium (MgO formation), and digestion of food (enzymatic breakdown into simpler molecules) are chemical changes where new substances are formed. Physical changes are reversible, while most chemical changes are irreversible. Exam tip: Remember, changes of state (melting, boiling, condensation) are physical changes unless a chemical reaction accompanies them.

Explanation:
Cracking is a petrochemical process where complex, heavy hydrocarbon molecules are broken down (cleaved) into lighter, more valuable molecules like gasoline and alkenes. This is achieved by applying high temperatures and pressures, often in the presence of a catalyst (catalytic cracking).