Mole Concept - JEE Advanced Previous Year Questions with Solutions

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Why Mole Concept Matters in JEE Advanced 

The mole concept is the foundation of physical chemistry. In JEE Advanced, it appears both as a standalone topic and as the entry point for questions on solutions, electrochemistry, and chemical equilibrium. According to the NTA's official JEE Advanced syllabi, mole concept falls under Physical Chemistry – Basic Concepts, a section that has contributed 1–3 questions in nearly every JEE Advanced paper since 2009.

What makes these questions tricky is not the formula — it is the unit conversion. Students who can mechanically apply the molarity formula still lose marks because they miss a density conversion from g/cm³ to kg/L, or confuse volume of solution with volume of solvent.

Mole Concept - JEE Advanced Previous Year Questions with Solutions

JEE Advanced Previous Year Questions of Chemistry with Solutions are available at eSaral. Practicing JEE Advanced Previous Year Papers Questions of Chemistry will help the JEE aspirants in realizing the question pattern as well as help in analyzing weak & strong areas. [esquestion] Given that the abundances of isotopes $^{54} \mathrm{Fe},^{56}$ Fe and $^{57}$ Fe are $5 \%, 90 \%$ and $5 \%$, respectively, the atomic mass of Fe is : (A) 55.85               (B) 55.95                (C) 55.75               (D) 56.05 #tag# [JEE 2009] #sol# (B) $\mathrm{M}_{\mathrm{AVg}}=\frac{\mathrm{M}_{1} \mathrm{X}_{1}+\mathrm{M}_{2} \times \mathrm{X}_{2}+\mathrm{M}_{3} \times \mathrm{X}_{3}}{\mathrm{x}_{1}+\mathrm{x}_{2}+\mathrm{x}_{3}}$ $=\frac{5 \times 54+56 \times 90+5 \times 57}{5+90+5}$ = 55.95 [/esquestion] [esquestion] Silver (atomic weight $=108 \mathrm{g} \mathrm{mol}^{-1}$ ) has a density of 10.5 g $\mathrm{cm}^{-3}$. The number of silver atoms on a surface of area $10^{-12} \mathrm{m}^{2}$ can be expressed in scientific notation as y ´ $10^{\mathrm{x}}$. The value of x is - #tag# [JEE 2010] #sol# 7 $\mathrm{d}=\frac{\text { mass }}{\mathrm{V}} \Rightarrow 10.5 \mathrm{g} / \mathrm{cm}^{3}$ means in $1 \mathrm{cm}^{3}=10.5 \mathrm{g}$ of $\mathrm{Ag}$ No of atom of $\mathrm{Ag}$ in $1 \mathrm{cm}^{3}=\frac{10.5}{108} \times \mathrm{N}_{\mathrm{A}}$ in $1 \mathrm{cm}, \mathrm{no}$ of atom of $\mathrm{Ag}=\left(\frac{10.5}{108} \times \mathrm{N}_{\mathrm{A}}\right)^{1 / 3}$ in $10^{-12} \mathrm{m}^{2}$ or $10^{-8} \mathrm{cm}^{2},$ No of atom of $\mathrm{Ag}$ $=\left(\frac{10.5 \mathrm{N}_{\mathrm{A}}}{108}\right)^{2 / 3} \times 10^{-8}=\left(\frac{1.05 \times 6.022 \times 10^{23}}{108}\right)^{2 / 3} \times 10^{-8}$ $=1.5 \times 10^{7}$ Hence $\mathrm{x}=7$ [/esquestion] [esquestion] Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is (A) 1.78 M          (B) 2.00 M             (C) 2.05 M              (D) 2.22 M #tag# [JEE 2011] #sol# (C) Vol of Solution $=\frac{\text { mass }}{\text { density }}$ $=\frac{1000+120}{1.15} \mathrm{mL}$ $=\frac{1120}{1.15} \mathrm{ml}$ Molarity $=\frac{120 / 60}{\frac{1120}{1.15}} \times 1000=2.05 \mathrm{M}$ [/esquestion] [esquestion] A compound $\mathrm{H}_{2} \mathrm{X}$ with molar weight of 80 g is dissolved in a solvent having density of 0.4 g /ml, Assuming no change in volume upon dissolution, the molality of a 3.2 molar solution is. #tag# [JEE 2014] #sol# 8 $\mathrm{V}_{\text {solvent }}=\mathrm{V}_{\text {solution }}$ 3.2 mol present in 1L solution (solvent) 3.2 mol / solvent $1000 \times 0.4=400 \mathrm{gm}$ $=.4 \mathrm{Kg}$ Molality $=\frac{3.2}{0.4}=8 \mathrm{m}$ [/esquestion] [esquestion] The mole fraction of a solute in a solution is 0.1. At 298 K, molarity of this solution is the same as its molality. Density of this solution at 298 K is 2.0 g $\mathrm{cm}^{-3}$. The ratio of the molecular weights of the solute and solvent, $\left(\frac{\mathrm{MW}_{\text {solute }}}{\mathrm{MW}_{\text {solikent }}}\right)$, is #tag# [JEE - ADV. 2016] #sol# 9 1 mole solution has 0.1 mole solute and 0.9 mole solvent Let $\mathrm{M}_{1}=$ Molar mass solute $\mathrm{M}_{2}=$ Molar mass solvent [/esquestion]

After practising Mole Concept - JEE Advanced PYQs (Chemistry), explore complete papers through the JEE Advanced PYQ collection.