JAMB - Chemistry (2008 - No. 40)
A hydrocarbon X with a molar mass of 26 consists of 92.3% carbon. What is its molecular formular?
C2H2
C3H3
C4H4
C5H5
Explanation
% of H2 = 100 - 92.3 = 7.7%
mole = Carbon [92.3 / 12] = 7.7
Hydrogen [7.7 / 1] = 7.7
divide with the lowest:
Carbon - 7.1 / 7.1 = 1
Hydrogen - 7.1 / 7.1 = 1
empirical formula = CH
(CH)n = 26
(12 + 1)n = 26
(13)n = 26
n = 26/13 = 2
molecular formula = C\(_2\)H\(_2\)
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