Class NEET 2026 ALL Q #1964
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
The amount of carbon dioxide evolved upon complete combustion of 116 g of n-butane is (Given: atomic mass in amu $H=1$, $C=12$ and $O=16$)
(A) 362 g
(B) 352 g
(C) 322 g
(D) 176 g
Correct Answer: B

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Detailed Solution

Step 1: Write the balanced chemical equation

The combustion of n-butane ($C_4H_{10}$) in oxygen is represented by the following balanced equation: $$2C_4H_{10} + 13O_2 \rightarrow 8CO_2 + 10H_2O$$

Step 2: Calculate the molar mass of n-butane

Molar mass of $C_4H_{10} = (4 \times 12) + (10 \times 1) = 48 + 10 = 58 \text{ g/mol}$.

Step 3: Determine the moles of n-butane

Given mass = 116 g. $$\text{Moles of } C_4H_{10} = \frac{116}{58} = 2 \text{ moles}$$

Step 4: Use stoichiometry to find moles of $CO_2$

From the balanced equation, 2 moles of $C_4H_{10}$ produce 8 moles of $CO_2$. Since we have exactly 2 moles of $C_4H_{10}$, we will produce 8 moles of $CO_2$.

Step 5: Calculate the mass of $CO_2$

Molar mass of $CO_2 = 12 + (2 \times 16) = 44 \text{ g/mol}$. $$\text{Mass of } CO_2 = 8 \text{ moles} \times 44 \text{ g/mol} = 352 \text{ g}$$

Final Answer: 352 g

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must translate a chemical word problem into a balanced stoichiometric equation and perform multi-step calculations.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the application of a specific algorithm (stoichiometry) to solve for a quantitative outcome.
Syllabus Audit: In the context of NEET, this is classified as COMPETENCY. It tests the fundamental ability to relate molar mass and chemical equations, which is a core requirement for the 'Some Basic Concepts of Chemistry' unit.