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

JEE Main 2026 — 2 April, Morning Shift — Question 41

The mass of iron converted into $\mathrm{Fe}_{3} \mathrm{O}_{4}$ by the action of 18 g of steam is : (Given : Molar mass of H, O and Fe are 1, 16 and $56 \mathrm{~g} \mathrm{~mol}^{-1}$ respectively)

Assume iron is present in excess :

Option A:
2.1 g
Option B:
4.2 g
Option C:
21 g
Option D:
42 g
Correct

Answer: D

Step-by-step solution

$3 \mathrm{Fe}(\mathrm{s})+4 \mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightarrow \mathrm{Fe}_{3} \mathrm{O}_{4}(\mathrm{~s})+4 \mathrm{H}_{2}(\mathrm{~g})$ $\mathrm{n}_{\text {steam }}=\frac{18}{18}=1$ $\mathrm{n}_{\mathrm{Fe}}$ required $=\frac{3}{4}$

\begin{aligned} & \text { mass of Fe required }=\frac{3}{4} \times 56 & \quad=42 \mathrm{gm} \end{aligned}

Answer key and solution verified before publishing.

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

Start with this question, then two more from the same chapter — with a tutor that explains every step. Free.

Solve a similar one free

Exam: JEE Main 2026
Paper: 2 April, Morning Shift
Subject: Chemistry
Chapter: Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry
Topic: Chemical Equations, Stoichiometry and Limiting Reagent