Avanine-Commuter - 9-5-2006 at 15:04
Hi. I need some help with this lab I'm currently working on.
First, I dissolved 3 grams of NaNO2 (sodium nitrite) in 10 mL of water. I have two of these NaNO2 solutions in two separate test tubes. I then brought
one to 0 degrees C in a beaker of ice and left the other one at room temperature. When I added 5mL of glacial acetic acid to the cold solution, the
top half of the solution bubbled and changed to a light blue color.
I'm thinking the color change occured due to nitrous acid, a product from this reaction.
NaNO2 + HC2H3O2 --> HNO2 + NaC2H3O2
My questions are:
1. Why did I have to bring the solution to 0 degrees celsius? Does the glacial acetic acid have to freeze before the reaction will occur? Or does the
temperature change a different aspect of the reaction?
2. Are my products correct from the reaction?
3. Why does the solution bubble? Is it boiling or is it just a part of the reaction?
4. What type of reaction is this? I think it's a double replacement, but is there a specific name for this reaction?
Thanks in advance.
chemoleo - 9-5-2006 at 15:21
You brought it to 0 deg C to avoid decomposition of HNO2 (nitrous acid) as it is thermally very unstable. The bubbles you saw are most like
decomposing HNO2, producing NO gas which reacts with air to produce NO2.
Yes your products are correct.
The reaction is no different to HCl reacting with Na2CO3, the stronger acid liberates the weaker one, and since H2CO3 is badly soluble in H2O, you get
CO2 gas...
Avanine-Commuter - 10-5-2006 at 14:21
Thanks for the help!