JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Some Basic Concepts of Chemistry

The mass of iron converted into

Fe_{3} O_{4}

by the action of 18 g of steam is :
(Given : Molar mass of H, O and Fe are 1, 16 and

56 g mol^{- 1}

respectively)

Assume iron is present in excess :

Answer: (D)

Solution

Iron reacts with steam as

3 Fe (s) + 4 H_{2} O (g) \to F e_{3} O_{4} (s) + 4 H_{2} (g)

. Moles of steam

= \frac{18}{18} = 1 mol

. By the stoichiometry,

4 mol

of steam consume

3 mol

of iron, so

1 mol

of steam consumes

\frac{3}{4} mol

of iron. The mass of iron converted is

\frac{3}{4} \times 56 = 42 g

JEE Main · 2026 · 02 Apr 2026 · Shift 1 · Single correct option