Some Basic Concepts Of Chemistry Question 132

Question: 23.2 g of an organic compound having molecular formula $ C _{n}{H _{2n+2}} $ is burnt in excess of $ O _2(g) $ initially taken in a 44.82 L steel vessel. Before reaction the gaseous mixture w at 273 K with pressure of 2 aim. After complete combustion and loss of considerable amount of heat the mixture of product and excess of had a temperature of 546 K and 4.6 atm pressure. The formula of compound is

Options:

A) $ C _5H _{12} $

B) $ C _6H _{10} $

C) $ C _3H _8 $

D) $ C _4H _{10} $

Show Answer

Answer:

Correct Answer: D

Solution:

[d] Idea This problem can be solved by using concept of ideal gas equation and chemical equation involved in combustion reaction. Students are advised to follow steps. • Write chemical equation involved in combustion of hydrocarbon. • Assume initial pressure = p • Calculate increased pressure • Then, calculate number of mole using ideal gas equation. Equation of combustion $ C _{n}H _2n _{+2}+( \frac{3n+1}{2} )O _2\xrightarrow{{}}nCO _2+(n+1)H _2O $ Initial pressure of $ C _{n}H _2n _{+2} $ is p (assumed) Increase in pressure $ =p[ (2n+1)-1-( \frac{3n+1}{2} ) ]=( \frac{n-1}{2} )p $

$ \because $ Mass of organic compound $ =14\times n+2 $ 546 K and 4.6 atm or 273 K 2.3 atm Increase
$ \Rightarrow $ $ 2.3-2=0.3 $ atm $ p=\frac{nRT}{V}=\frac{23.2}{M}\times ( \frac{0.0821\times 273}{44.82} ) $

$ =\frac{23.2}{M}\times \frac{0.5}{44.82} $

$ =\frac{116}{(14n+2)}\times \frac{(n-1)}{2} $ also $ =\frac{(n-1)}{2}\times \frac{11.6}{14n+2}=0.3 $ On solving, $ n=4 $ So, compound will be $ C _4{H _{4\times 2+2}}\Rightarrow C _4H _{10} $



NCERT Chapter Video Solution

Dual Pane