Chapter 5 2024/2025

a) Potassium chlorate, KClO3 decomposes upon heating as below:

2 KClO3 (s) → 2 KCl (s) + 3 O2 (g)

When a sample of KClO3 is heated, 240 mL of oxygen gas with pressure 755 torr is collected over water at 26 oC. Calculate the mass of the decomposed KClO3.  [Pressure of water vapour at 26 oC is 25 torr] 

[5 Marks]    

b) Pentane C5H12 is a liquid whereas methane, CH4 is a gas at room temperature. Explain the difference in physical state of both hydrocarbons based on intermolecular forces.  

[4  Marks]