Class JEE Chemistry ALL Q #1170
COMPETENCY BASED
APPLY
4 Marks 2026 JEE Main 2026 (Online) 21st January Morning Shift MCQ SINGLE
80 mL of an organic compound is mixed with 264 mL of $O_{2}$ and ignited. It gives 224 mL of gaseous mixture at NTP. After passing through KOH, 64 mL of gas remains. The organic compound is:
(A) $C_{2}H_{4}$
(B) $C_{2}H_{2}$
(C) $C_{4}H_{10}$
(D) $C_{3}H_{6}$

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Step-by-Step Solution

Let the organic compound be $C_xH_y$. The combustion reaction can be written as:

$C_xH_y + (x + \frac{y}{4})O_2 \rightarrow xCO_2 + \frac{y}{2}H_2O$

Given:

Volume of organic compound = 80 mL

Volume of $O_2$ = 264 mL

Total volume of gaseous mixture = 224 mL

Volume of gas remaining after passing through KOH = 64 mL (This is $O_2$ remaining)

Volume of $CO_2$ absorbed by KOH = 224 - 64 = 160 mL

From the stoichiometry of the reaction:

80 mL of $C_xH_y$ produces 160 mL of $CO_2$

Therefore, $x = \frac{160}{80} = 2$

Volume of $O_2$ used = 264 - 64 = 200 mL

From the stoichiometry:

$x + \frac{y}{4} = \frac{200}{80} = 2.5$

Since $x = 2$:

$2 + \frac{y}{4} = 2.5$

$\frac{y}{4} = 0.5$

$y = 2$

Therefore, the organic compound is $C_2H_2$.

Correct Answer: $C_{2}H_{2}$<\/strong>

AI Suggestion: Option B

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply their knowledge of stoichiometry, gas laws, and chemical reactions to determine the molecular formula of the organic compound. They must use the given volumes to calculate the moles of reactants and products and then deduce the formula.
Knowledge Dimension: PROCEDURAL
Justification: The question requires a series of steps to solve, including writing a balanced chemical equation, using stoichiometry to relate volumes of reactants and products, and solving for the unknown coefficients in the molecular formula. This involves applying a specific algorithm or method.
Syllabus Audit: In the context of JEE, this is classified as COMPETENCY. The question requires the application of chemical principles to solve a problem, rather than simply recalling facts or definitions. It assesses the student's ability to analyze the given information and apply relevant concepts to arrive at the correct answer.