Chemistry - Mole Concept Question with Solution | TestHub
An organic compound having molecular mass 60 is found to contain and while rest is oxygen. On heating it gives alongwith a solid residue. The solid residue give violet colour with alkaline copper sulphate solution. The compound is
Options:
Answer:
Solution:
To determine the compound, first calculate the empirical formula from the given percentages.
C = 20%, H = 6.67%, N = 46.67%.
Oxygen percentage = .
Moles of C =
Moles of H =
Moles of N =
Moles of O =
Divide by the smallest number of moles (1.67):
C =
H =
N =
O =
Empirical formula is CH₄N₂O.
Empirical formula mass = .
Since the molecular mass is 60, the molecular formula is also CH₄N₂O.
Now, let's check the options:
A. CH₃NCO (Methyl isocyanate): C=2, H=3, N=1, O=1. Molecular mass = .
B. CH₃CONH₂ (Acetamide): C=2, H=5, N=1, O=1. Molecular mass = .
C. (NH₂)₂CO (Urea): C=1, H=4, N=2, O=1. Molecular mass = . This matches the calculated molecular formula.
D. CH₃CH₂CONH₂ (Propanamide): C=3, H=7, N=1, O=1. Molecular mass = .
Urea ((NH₂)₂CO) on heating decomposes to ammonia (NH₃) and a solid residue, biuret. Biuret gives a violet color with alkaline copper sulfate solution (biuret test).
The final answer is .