JEE Main & Advanced Chemistry Some Basic Concepts of Chemistry / रसायन की कुछ मूलभूत अवधारणाएँ Sample Paper Topic Test - Some Basic Concepts of Chemistry

  • question_answer
    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

    A) \[{{C}_{5}}{{H}_{12}}\]

    B) \[{{C}_{6}}{{H}_{10}}\]

    C) \[{{C}_{3}}{{H}_{8}}\]

    D) \[{{C}_{4}}{{H}_{10}}\]

    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
    \[{{C}_{n}}{{H}_{2n}}_{+2}+\left( \frac{3n+1}{2} \right){{O}_{2}}\xrightarrow{{}}nC{{O}_{2}}+(n+1){{H}_{2}}O\]
    Initial pressure of \[{{C}_{n}}{{H}_{2n}}_{+2}\] is p (assumed)
    Increase in pressure
    \[=p\left[ (2n+1)-1-\left( \frac{3n+1}{2} \right) \right]=\left( \frac{n-1}{2} \right)p\]
    \[\because \] 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
    \[p=\frac{nRT}{V}=\frac{23.2}{M}\times \left( \frac{0.0821\times 273}{44.82} \right)\]
    \[=\frac{23.2}{M}\times \frac{0.5}{44.82}\]
    \[=\frac{116}{(14n+2)}\times \frac{(n-1)}{2}\]
    also       \[=\frac{(n-1)}{2}\times \frac{11.6}{14n+2}=0.3\]
    On solving, \[n=4\]
    So, compound will be \[{{C}_{4}}{{H}_{4\times 2+2}}\Rightarrow {{C}_{2}}{{H}_{10}}\]
    TEST Edge. JEE Main includes this type of question in exam to judge the knowledge as well as numerical aptitude of students. So, students are advised to solve the question as much as possible.


You need to login to perform this action.
You will be redirected in 3 sec spinner