ICSE Class 10 Chemistry 2019 Solved Paper

Question : 81

Total: 86

Find the empirical formula and the molecular formula of an organic compound from the data given below :
C=75.92%,H=6.32%‌ and ‌N=17.76%
The vapour density of the compound is 39.5 .
[C=12,H=1,N=14]

Solution:

C	‌	H	‌	N
75.92	‌	6.32	‌	17.76
75.92∕12	‌	6.32∕1	‌	17.76∕14
6.32	‌	6.32	‌	1.26
6.32∕1.26	‌	6.32∕1.26	‌	1.26∕1.26
5.01	‌	5.01	‌	1
5	:	5	:	1

Empirical formula : C5H5N
Empirical formula Mass
‌=C5H5N
‌=12×5+1×5+14
‌=60+5+14=79
‌ V.D. ‌=39⋅5‌‌
‌ Mol. Mass ‌‌=2×‌ V.D. ‌
‌=2×39.5=79
n‌=‌

‌ Mol. Mass ‌

‌ Emp. formula Mass ‌

‌=‌

=1
Molecular formula
‌=(‌ Empirical formula ‌)n
‌=C5H5N×1
‌=C5H5N

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