Lecture on Chemical Reactions Involving Barium Hydroxide and Ammonium Chloride

Introduction

• Demonstration involving barium hydroxide and ammonium chloride.
• Aim: To observe an endothermic reaction.

Materials Used

• Barium hydroxide
• Ammonium chloride
• Wooden block (to be used in part of the demonstration)
• Water

Experimental Setup

• Barium hydroxide and ammonium chloride will be mixed together.
• Reaction is expected to be endothermic.

Process and Observations

• Mixing Process:

  • The two substances are mixed together carefully.
  • Expected result: Subtle reaction, not explosive (characteristic of an exothermic reaction).

• Observations During Reaction:

  • As the substances mix, they begin to clump together.
  • Reaction produces water, changing the consistency from powders to liquid.
  • Ammonia is released, noted by its distinctive, tangy smell.
  • The reaction is endothermic, absorbing heat from the surroundings, causing the mixture to get cold.

Results

• Temperature Change:
  • The temperature drops significantly.
  • The water on the wooden block freezes due to the heat absorbed by the reaction.
  • Example: Thermometer shows a drop to around -5°C, indicating significant cooling.

Additional Notes

• Safety Considerations:
  • Ammonia release is noticeable and can be unpleasant.
  • Caution advised when handling the mixture after temperature drop.
  • Formation of ice crystals noted on the reaction setup.

Conclusion

• The reaction between barium hydroxide and ammonium chloride effectively demonstrates an endothermic process.
• Significant cooling effect observed, with practical implications highlighted by the freezing of water on the wooden block.