Question on: JAMB Chemistry - 2009

Here's the breakdown of why curve Z represents the evolution of oxygen:

• The Reaction: The equation 2KClO3(s) → 2KCl(s) + 3O2(g) shows the decomposition of potassium chlorate (KClO3) into potassium chloride (KCl) and oxygen gas (O2).
• Oxygen Production: Oxygen gas is a product of this reaction. As the reaction proceeds, the amount of oxygen produced increases.
• Curve Analysis:
  • Curve X and R are starting from an amount of oxygen and decreasing, not increasing.
  • Curve Y is constant, meaning no oxygen is being produced.
  • Curve Z starts at zero oxygen and increases with time, which matches the oxygen production.