For the reaction, CaCO 3 + 2HCl rightarrow CaCl 2 + H 2O + CO 2 . If 90\, g of CaCO 3 is added to 300\, mL of HCl which contains 38.55\% HCl by mass and has density 1.13\, g\,mL -1 , then which of the following option is correct? (Given molar masses: H =1 , Cl =35.5 , Ca =40 , O =16\, g\,mol -1 )

64.97\, g of HCl remains unreacted

32.85\, g of CaCO 3 remains unreacted

60.32\, g of HCl remains unreacted

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

JEE Main 2026 — 28 January, Evening Shift — Question 62

For the reaction, $\mathrm{CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2}$ . If $90\,\mathrm{g}$ of $\mathrm{CaCO_3}$ is added to $300\,\mathrm{mL}$ of $\mathrm{HCl}$ which contains $38.55\%$ $\mathrm{HCl}$ by mass and has density $1.13\,\mathrm{g\,mL^{-1}}$ , then which of the following option is correct?

(Given molar masses: $\mathrm{H}=1$ , $\mathrm{Cl}=35.5$ , $\mathrm{Ca}=40$ , $\mathrm{O}=16\,\mathrm{g\,mol^{-1}}$ )

Option A:
$64.97\,\mathrm{g}$ of $\mathrm{HCl}$ remains unreacted
Correct
Option B:
$32.85\,\mathrm{g}$ of $\mathrm{CaCO_3}$ remains unreacted
Option C:
$97.30\,\mathrm{g}$ of $\mathrm{HCl}$ reacted
Option D:
$60.32\,\mathrm{g}$ of $\mathrm{HCl}$ remains unreacted

Answer: A

Step-by-step solution

Given reaction: $\mathrm{CaCO_3 + 2HCl \rightarrow CaCl_2 + H_2O + CO_2}$

Mass of $\mathrm{HCl}$ solution $= 300 \times 1.13 = 339\,\mathrm{g}$

Mass of pure $\mathrm{HCl}$ $= 0.3855 \times 339 = 130.68\,\mathrm{g}$

Molar mass of $\mathrm{HCl}$ $= 36.5\,\mathrm{g\,mol^{-1}}$

Moles of $\mathrm{HCl}$ $= \frac{130.68}{36.5} = 3.58\,\mathrm{mol}$

Molar mass of $\mathrm{CaCO_3}$ $= 40 + 12 + 48 = 100\,\mathrm{g\,mol^{-1}}$

Moles of $\mathrm{CaCO_3}$ $= \frac{90}{100} = 0.90\,\mathrm{mol}$

Required $\mathrm{HCl}$ $= 2 \times 0.90 = 1.80\,\mathrm{mol}$

Thus $\mathrm{HCl}$ is in excess.

Mass of $\mathrm{HCl}$ reacted $= 1.80 \times 36.5 = 65.7\,\mathrm{g}$

Mass of $\mathrm{HCl}$ remaining $= 130.68 - 65.7 = 64.98\,\mathrm{g}$

Hence, option (A) is correct.

Answer key and solution verified before publishing.

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Exam: JEE Main 2026
Paper: 28 January, Evening Shift
Subject: Chemistry
Chapter: Some Basic Concepts of Chemistry (Mole Concept) + Stoichiometry
Topic: Chemical Equations, Stoichiometry and Limiting Reagent