Chemistry · Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry

JEE Main 2026 — 6 April, Morning Shift — Question 46

An oxide of iron contains $69.9 \%$ iron, its empirical formula, is : (Given : Molar mass of Fe and O are 56 and $16 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively.)

Option A:
FeO
Option B:
$\mathrm{Fe}_{2} \mathrm{O}_{3}$
Correct
Option C:
$\mathrm{Fe}_{3} \mathrm{O}_{4}$
Option D:
$\mathrm{FeO}_{3}$

Answer: B

Step-by-step solution

$\begin{array}{c c} \text{Fe} & \text{Oxygen} \\ \text{Moles:} & \dfrac{69.9}{56} \quad \dfrac{30.1}{16} \\ \text{Molar ratio:} & 1 : 1.5 \\ \text{Molar ratio:} & 2 : 3 \end{array}$ Answer : $\mathbf{F e}_{\mathbf{2}} \mathbf{O}_{\mathbf{3}}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 6 April, Morning Shift
Subject: Chemistry
Chapter: Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry
Topic: Percentage composition & Empirical Formula