Question

Water containing hydrogen carbonate, HCO3− and calcium Ca2+ ions, is said to be hard water

1. Describe one way in which HCO3− ions get into river waler (1 mark)
2. Explain the disadvantage of using this type of water in boilers.  (2 marks)

Answer 1

1.   
   • CO₂  dissolves in rain water to form Carbonic acid 
   • Carbonic acid reacts with carbonate rock/Ca and Mg forming hydrogen carbonates of Ca and Mg that gets into rivers. 
2.  The CaHCO₃ and MgCO₃ decomposes forming CaCO₃/scales/fur  lining the boilers and causing poor thermal conductivity/reducing efficiency.