Lecture on Ionic Equations and Gas Evolution Reactions

Introduction to Ionic Equations

• From a molecular equation, we can derive total and net ionic equations.
• Example reaction: Na2CO3 + HBr
  • Both are aqueous and can be broken into ions.

Ion Breakdown

• Na2CO3:
  • Na: Group 1A, charge +1.
  • CO3: Carbonate ion, CO3 with a charge of 2-.
• HBr:
  • H: Group 1A, charge +1.
  • Br: Group 7A, charge -1.

Partner Switching

• Combine ions to form new compounds:
  • Na+ and Br- form NaBr.
  • H+ and CO3 2- form H2CO3.

Solubility Rules

• NaBr: Soluble, aqueous.
• Carbonates with Group 1A ions are usually soluble.
  • H2CO3 is aqueous.

Gas Evolution Reactions

• H2CO3 (Carbonic acid) breaks down to:
  • H2O (liquid) + CO2 (gas)
• Gas Evolution: Formation of gas as a product.
  • CO2 is a common gas formed.

Other Gas Evolution Reactions

• H2SO3 (Sulfurous acid) decomposes to:
  • H2O (liquid) + SO2 (gas)
• NH4OH (Ammonium hydroxide) decomposes to:
  • H2O (liquid) + NH3 (gas)

Balancing the Equation

• Ensure all elements are balanced on both sides.
  • Adjust coefficients as necessary.

Conclusion

• Reactions resulting in liquid and gas indicate that a reaction occurs.
• Always check for decomposition in products like H2CO3, H2SO3, and NH4OH which lead to gas evolution.
• Example balanced equation after adjustment:
  • Consideration was given to ensure each element is balanced across the equation, accommodating the formation of gas and liquid products.