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JAMB Chemistry 2024 Paper

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Question : 10

Total: 138

An organic compound contains 53.1% Carbon, 6.2% Hydrogen, 12.4% Nitrogen, and 28.3% Oxygen by mass. What is the molecular formula of the compound if its vapour density is 56.5? [ C =12, H = 1, N = 14, O = 16].

C $_{5}$ H $_{7}$ NO $_{2}$
C $_{5}$ H $_{6}$ NO $_{2}$
C $_{3}$ H $_{6}$ NO $_{2}$
C $_{3}$ H $_{7}$ NO $_{2}$

Solution:

C H N O

$\frac{53.1}{12}$ $\frac{6.2}{1}$ $\frac{12.4}{14}$ $\frac{28.3}{16}$

$\frac{4.425}{0.886}$ $\frac{6.2}{0.886}$ $\frac{0.886}{0.886}$ $\frac{1.769}{0.886}$

5 : 7 : 1 : 2

C $_{5}$ H $_{7}$ N O $_{2}$ - Empirical formula

(Empirical formula) n = Molecular formula

(C $_{5}$ H $_{7}$ NO $_{2}$ )n = 2 x vapour density

([12x5] + [1x7] + 14 + [16x2] ) n = 2 x 56.5

113n = 113

n = $\frac{113}{113}$

n = 1

Therefore, the molecular formula is C $_{5}$ H $_{7}$ NO $_{2}$

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