Barium hydroxide –ammonium thiocyanate reaction seriously endothermic

Barium hydroxide –ammonium thiocyanate reaction seriously endothermic! Also a great one for observations.

Ba(OH)₂^.8H₂O (s) + 2 NH₄SCN (s)

--> Ba(SCN)₂ (s) + 10 H₂O (l) + 2 NH₃ (g)

To use this reaction as a demonstration:

• 
  32g barium hydroxide octahydrate
  
• 
  17g ammonium thiocyanate (or could use ammonium nitrate or ammonium chloride)
  
• 
  250 ml beaker
  
• 
  stirring rod
  
• 
  wood block or piece or card
  
• 
  thermometer-digital is good
  
• 
  some wet litmus paper if you want to show gas is basic
  

Method:

• 
  Smear some water over a wood block or piece of card or lab mat
  
• 
  Pour the barium hydroxide and ammonium thiocyanate into the beaker and stir.
  
• 
  The smell of ammonia should become evident within seconds. If you hold a piece of wet litmus paper over the reaction mixture in the flask, you can see that the gas produced by the reaction is basic.
  
• 
  Liquid will be produced, so the mixture will turn slushy as the reaction proceeds.
  
• 
  If you set the flask on a damp block of wood or piece of cardboard while performing the reaction you can freeze the bottom of the flask to the wood or paper. You can touch the outside of the beaker, but don't hold it in your hand – better to have the digital thermometer giving the dramatic fall in temperature.
  
• 
  When you are finished, the contents of the flask can be washed down the sink with plenty of water. Avoid skin contact. If you get any solution on your skin, rinse it off straight away with water.
  

http://www.youtube.com/watch?v=yTzcoyzPQE0

is a nice video of this.

Lynda Keer- Burnside HS 2009