Some Basic Concepts Of Chemistry Question 36
Question: An organic compound whose empirical and molecular formula are same, contains 20% carbon, 6.7% hydrogen, 46.7% nitrogen and the rest oxygen. On heating it yields ammonia, leaving a solid residue. The solid residue gives a violet colour with dilute solution of alkaline copper sulphate. The organic compound is
Options:
A) $ NH _2COONH _4 $
B) $ HCOONH _4 $
C) $ NH _2NHCHO $
D) $ NH _2CONH _2 $
Show Answer
Answer:
Correct Answer: D
Solution:
[d]
| Element | Percentage | Atomic mass | Relative no. of atoms | Simplest ratio |
|---|---|---|---|---|
| C | 20% | 12 | 1.66 | 1 |
| H | 6.7% | 1 | 6.7 | 4 |
| N | 46.7% | 14 | 3.33 | 2 |
| O | 26.6% | 16 | 1.66 | 1 |
Empirical formula = Molecular formula $ =CH _4N _2O,or,NH _2CONH _2 $
$ H _2NCONH _2+H _2NCONH _2\xrightarrow{\Delta } $ $ \underset{\text{biuret,}}{\mathop{H _2NCONHCONH _2}},+NH _3 $
When an aqueous solution of biuret is treated with dilute sodium hydroxide and a drop of copper sulphate, a violet colour is produced. This test is known as biuret test, and is characteristic of compounds having the group $ -CONH- $
