why is soda-lime test not considered a confirmatory test for presence of nitrogen?

Question

we did an experiment in our chem lab wherein we added grinded soda-lime and blended mongo and then heated it. We put moistened litmus paper at a tip of a stirring rod and it turned blue. The questions on our manual are confusing and i'm really having a hard time i need your help...

these are the questions:

1. What is the role of soda-lime in the reaction?

2. Write the chemical equations involved in:
a) reaction with soda-lime
b) reaction with litmus papers

3. why is the soda-lime test NOT considered a confirmatory test for the presence of nitrogen?

please.. i need infos.. i'm really confused.. >.<
thanks!

^_T kc

Answer 1

Lancenigo di Villorba (TV), Italy

The reactive you used is a solid mixture that you formed by dry grinding of Soda and Lime...this latter terms mean SODIUM CARBONATE (e.g. Soda as Na2CO3) and CALCIUM HYDROXIDE (e.g. Lime as Ca(OH)2), two bases within Inorganic Chemistry.
Clearly, this reactives get a chemical action as bases against some acidic stuffs inside your analyte, e.g. the Mongo.
In effect, some phenomena run so you remarked vapours able to turn bluish the Moistened Litmus Paper : since you added some water drops to litmus paper, you have to think to another acid-base reaction, this time upon the paper-strip.

QUESTION 1)
Soda-Lime acts as strong bases and they lead an Acid-Base Reaction, the latter permitted by dry and hot conditions.
On other terms, the Mongo has to contain several acidic compound able to react against Soda-Lime.
I will assume the Mongo as containing Ammonium Salt, e.g. Ammonium Chloride.

QUESTION 2)
Reaction with Soda-Lime

Na2CO3(s) + 2 NH4Cl(s) --->
---> 2 NaCl(s) + 2 NH3(g) + 2 CO2(g) + 2 H2O(g)
Ca(OH)2(s) + 2 NH4Cl(s) --->
---> CaCl2(s) + 2 NH3(g) + 2 H2O(g)

Reaction with Litmus Paper

NH3(g) + H2O(aq) ---> NH4+(aq) + OH-(aq)

QUESTION 3)
Soda-Lime Test cannot be a confirmatory test for Nitrogen : do you know Nitrate and Nitrite Salts? Do you know them as NO3- and NO2- anions?
They are common Nitrogen Compounds but they show anyone phenomenon when you treat them in the described test.

I hope this helps you.

Answer 2

Soda Lime Test

Answer 3

Litmus tests for acid/base.

You got a blue colour, so you had a volatile base. Obviously ammonia or perhaps an amine.

The soda lime has reacted with the mongo to make ammonia,so there must have been nitrogen in the mongo.

This seems to me to definitely confirm nitrogen in the mongo.