[constant thinker]

This is more for my own satisfaction but...

We did a lab where we had to identify various white powders. We were given the 6 possibilities of the 6 powders. For the sample that is ammonium chloride according to the teacher, I got results that I don't think could be ammonium chloride. My results were that it was soluble in water, which it is; it's basic according to a phenolphthalein test (It turned pink), I'm pretty sure it's acidic though; and lastly it burned when it was introduced to a flame.

Now for the pH test, I know that has to be a dead a give away that it isn't ammonium chloride because doesn't it dissociate into NH₃ and HCl.? That would make it acidic. Then when it burned when exposed to a flame. Doesn't it sublime somewhere around 300°C?


I just want to hear from someone else that this can't be ammonium chloride. I thought it was sucrose, because upon retesting, and testing with other things (addition of I₂ to test for starch, addition of potassium nitrate to test for KI, among other things). I don't know about the pH of sucrose though, but it looked like the best bet.

I also haven't looked up the wikipedia information because I want my data to be reviewed by other people.

[Borek]

Should be slightly acidic, NH⁴⁺ is a weak acid and it dissociates lowering solution pH.

As for burning... I am not quite sure how it will behave. Ammonia is flammable. At high temperature you may expect thermal decomoposition of the salt, so you have some free ammonia. But whether it will burn in the air in the presence of gaseous hydrochloride - I have no idea.

[constant thinker]

The fact that it phenolphthalein turned pink when it was added to a solution with it in it just makes me think logically that it can't be ammonium chloride. I know we repeated the phenolphthalein test 3 times. Each time it turned pink. I also tested it in the distilled water we were using just to be safe (it stayed clear).

I guess it could have also been possible that the sample was contaminated.

Another sample sublimed when we heated it. We had no other possibilities that sublime (sodium hydrogen carbonate, potassium iodide, starch, sucrose, and calcium oxide were the other possibilities).

When I heated the sample I kept it at the top of the bunsen burner flame, so I'm not thinking it got hot enough to decompose. For the heck of it though once we had finished, I reacted some of the calcium oxide with water to produce calcium hydroxide. I then added that to my suspected ammonium chloride, heated very gently (I made a "camp fire" flame with the bunsen burner for this), and got a reaction. The gas that came off of it smelt like ammonia (I removed it from the flame area so I could check for ammonia, and not have it burn off).

Thanks for your response though Borek.

[pantone159]

So the sample that sublimed was the one that reacted with CaO to make ammonia?

My guess, is that you are right, and your teacher is not.