\(120 \;g\) of an organic compound that contains only carbon and hydrogen gives \(330\) \(g\) of \(CO_2\) and \(270\) \(g\) of water on complete combustion. The percentage of carbon and hydrogen, respectively are
- 25 and 75
- 40 and 60
- 60 and 40
- 75 and 25
The Correct Option is D
Solution and Explanation
Mass of organic compound = \(120\) \(g\)
Mass of \(CO_2 = 330\) \(g\)
Moles of \(CO_2 = \frac{330}{44}= 7.5\)
Mass of carbon = \(7.5 × 12 = 90\) \(gm\)
Percentage of Carbon = \(\frac{90}{120} × 100 = 75\%\)
Mass of \(H_2O = 270\) \(g\)
Moles of \(H_2O = \frac{270}{18}= 15\)
Mass of hydrogen = \(15 × 2 = 30\) \(gm\)
Percentage of Hydrogen = \(\frac{30}{120} × 100 = 25\%\)
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Concepts Used:
Structure of Organic Compounds
The three structural formulas – complete structure, condensed structure, and bond line structural formulas are explained below:
Complete Structural Formula-
The Lewis dot structure is considered as the complete structural formula. In Lewis structure, the covalent bonds in the compound are denoted by a dash (―). This helps to emphasize the number of bonds formed by the electrons. Every single bond, a double bond, and a triple bond are represented by one dash, double dash, and triple dash respectively. It illustrates every single bond formed between every atom in the compound, thus called complete structural formula.
Condensed Structural Formula-
Since complete structural formula consumes much time and space to represent the structure, we can condense them. This is the condensed structural formula, where replacing some dashes/bonds by a number of identical groups attached to an atom by a subscript.
Bond Line Structural Formula-
A bond lines structural formula is another way of structural representation of organic compounds. Here, every bond is represented as a line in a zigzag manner. If not specified, every terminal is assumed to be a methyl (-CH3) group.