JEE Main Chemistry — Physical Chemistry previous year questions with solutions.
$1.2\mathrm{mL}$ of acetic acid is dissolved in water to make $2.0L$ of solution. The depression in freezing point observed for this strength of acid is $0.0198^{\circ}C$. The percentage of dissociation of the acid is (Nearest integer) [Given : Density of acetic acid is $1.02g{\mathrm{mL}}^{-1}$ Molar mass of acetic acid is $60g{\mathrm{mol}}^{-1}$ ${K}_{f}({H}_{2}O)=1.85K\mathrm{kg}{\mathrm{mol}}^{-1}$]
$\mathrm{CNG}$ is an important transportation fuel. When $100\mathrm{gCNG}$ is mixed with $208g$ oxygen in vehicles, it leads to the formation of ${\mathrm{CO}}_{2}$ and ${H}_{2}O$ and produces large quantity of heat during this combustion, then the amount of carbon dioxide, produced in grams is [nearest integer] [Assume CNG to be methane]
Solute A associates in water. When $0.7g$ of solute $A$ is dissolved in $42.0g$ of water, it depresses the freezing point by $0.2^{\circ}C$. The percentage association of solute $A$ in water, is [Given: Molar mass of $A=93g{\mathrm{mol}}^{-1}$. Molal depression constant of water is $1.86K\mathrm{kg}{\mathrm{mol}}^{-1}$]
The osmotic pressure exerted by a solution prepared by dissolving $2.0g$ of protein of molar mass $60\mathrm{kg}{\mathrm{mol}}^{-1}$ in $200\mathrm{mL}$ of water at $27^{\circ}C$ is____$\mathrm{Pa}$. [integer value] (use $R=0.083L$ bar ${\mathrm{mol}}^{-1}{K}^{-1}$)
The vapour pressures of two volatile liquids $A$ and $B$ at $25^{\circ}C$ are $50$ Torr and $100$ Torr, respectively. If the liquid mixture contains $0.3$ mole fraction of $A$, then the mole fraction of liquid $B$ in the vapour phase is $\frac{x}{17}$. The value of $x$ is
Resistance of a conductivity cell (cell constant $129{m}^{-1}$) filled with $74.5\mathrm{ppm}$ solution of $\mathrm{KCl}$ is $100\Omega$ (labelled as solution $1$). When the same cell is filled with $\mathrm{KCl}$ solution of $149\mathrm{ppm}$, the resistance is $50\Omega$ (labelled as solution $2$). The ratio of molar conductivity of solution $1$ and solution $2$ is i.e. $\frac{{\wedge }_{1}}{{\wedge }_{2}}=x\times {10}^{-3}$. The value of $x$ is____Given, molar mass of $\mathrm{KCl}$ is $74.5g{\mathrm{mol}}^{-1}$)
The solubility product of a sparingly soluble salt ${A}_{2}{X}_{3}$ is $1.1\times {10}^{-23}$. If specific conductance of the solution is $3\times {10}^{-5}{\mathrm{Sm}}^{-1}$, the limiting molar conductivity of the solution is $x\times {10}^{-3}S{m}^{2}{\mathrm{mol}}^{-1}$. The value of $x$ is
In a cell, the following reactions take place ${\mathrm{Fe}}^{2+}\rightarrow {\mathrm{Fe}}^{3+}+{e}^{-}{{E}^{o}}_{{\mathrm{Fe}}^{3+}/{\mathrm{Fe}}^{2+}}=0.77V$ $2{I}^{-}\rightarrow {I}_{2}+2{e}^{-}{E}_{{I}_{2}/{I}^{-}}^{0}=0.54V$ The standard electrode potential for the spontaneous reaction in the cell is $x\times {10}^{-2}V\mathrm{at}298K$. The value of $x$ is - (Nearest Integer)
The quantity of electricity in Faraday needed to reduce $1\mathrm{mol}$ of ${\mathrm{Cr}}_{2}{O}_{7}^{2-}$ to ${\mathrm{Cr}}^{3+}$ is
If the wavelength for an electron emitted from $H-$ atom is $3.3\times {10}^{-10}m$, then energy absorbed by the electron in its ground state compared to minimum energy required for its escape from the atom, is____times. [Given : $h=6.626\times {10}^{-34}\mathrm{Js}$, Mass of electron $=9.1\times {10}^{-31}$]
For a reaction at equilibrium $A(g)\rightleftharpoons B(g)+\frac{1}{2}C(g)$ the relation between dissociation constant $(K)$, degree of dissociation $(\alpha )$ and equilibrium pressure $(p)$ is given by :
Chlorophyll extracted from the crushed green leaves was dissolved in water to make $2L$ solution of $\mathrm{Mg}$ of concentration $48 \mathrm{ppm}$. The number of atoms of $\mathrm{Mg}$ in this solution is $x\times {10}^{20}$ atoms. The value of $x$ is (Nearest Integer) (Given : Atomic mass of $\mathrm{Mg}$ is $24g{\mathrm{mol}}^{-1}$, ${N}_{A}=6.02\times {10}^{23}{\mathrm{mol}}^{-1}$)
$17.0g$ of ${\mathrm{NH}}_{3}$ completely vapourises at $-33.42^{\circ}C$ and $1$ bar pressure and the enthalpy change in the process is $23.4\mathrm{kJ}{\mathrm{mol}}^{-1}$. The enthalpy change for the vapourisation of $85g$ of ${\mathrm{NH}}_{3}$ under the same conditions is $\mathrm{kJ}$.
$2.4g$ coal is burnt in a bomb calorimeter in excess of oxygen at $298K$ and $1\mathrm{atm}$ pressure. The temperature of the calorimeter rises from $298K$ to $300K$. The enthalpy change during the combustion of coal is $-x\mathrm{kJ}{\mathrm{mol}}^{-1}$. The value of $x$ is_____(Given : Heat capacity of bomb calorimeter $20.0{\mathrm{kJK}}^{-1}$. Assume coal to be pure carbon)
The molar heat capacity for an ideal gas at constant pressure is $20.785J{K}^{-1}{\mathrm{mol}}^{-1}$. The change in internal energy is $5000J$ upon heating it from $300K$ to $500K$. The number of moles of the gas at constant volume is____ (Given: $R=8.314J{K}^{-1}{\mathrm{mol}}^{-1}$)
When $5$ moles of $\mathrm{He}$ gas expand isothermally and reversibly at $300K$ from $10$ litre to $20$ litre, the magnitude of the maximum work obtained is $J$. [nearest integer ] (Given : $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$ and $\mathrm{log}2=0.3010$)
$A$ fish swimming in water body when taken out from the water body is covered with a film of water of weight $36g$. When it is subjected to cooking at $100^{\circ}C$, then the internal energy for vaporization in ${\mathrm{kJmol}}^{-1}$ is integer] [Assume steam to be an ideal gas. Given ${\Delta }_{\mathrm{vap}}{H}^{\ominus }$ for water at $373K$ and $1$ bar is $41.1\mathrm{kJ}{\mathrm{mol}}^{-1}:R=8.31J{K}^{-1}{\mathrm{mol}}^{-1}$]
For complete combustion of methanol ${\mathrm{CH}}_{3}\mathrm{OH}(l)+\frac{3}{2}{O}_{2}(g)\rightarrow {\mathrm{CO}}_{2}(g)+2{H}_{2}O(l)$ the amount of heat produced as measured by bomb calorimeter is $726\mathrm{kJ}{\mathrm{mol}}^{-1}$ at $27^{\circ}C$. The enthalpy of combustion for the reaction is $-x\mathrm{kJ}{\mathrm{mol}}^{-1}$, where $x$ is integer) (Given : $R=8.3{\mathrm{JK}}^{-1}{\mathrm{mol}}^{-1}$)
For combustion of one mole of magnesium in an open container at $300K$ and $1$ bar pressure, ${\Delta }_{C}{H}^{\ominus }=-601.70\mathrm{kJ}{\mathrm{mol}}^{-1}$, the magnitude of change in internal energy for the reaction is $\mathrm{kJ}$. (Nearest integer) (Given : $R=8.3J{K}^{-1}{\mathrm{mol}}^{-1}$)
The standard free energy change $(\Delta G^{\circ})$ for $50%$ dissociation of ${N}_{2}{O}_{4}$ into ${\mathrm{NO}}_{2}$ at $27^{\circ}C$ and $1\mathrm{atm}$ pressure is $-xJ{\mathrm{mol}}^{-1}$. The value of $x$ is $-.....J$. (Nearest Integer) [Given : $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1},\mathrm{log}1.33=0.1239\mathrm{ln}10=2.3$]
At $298K$, the equilibrium constant is $2\times {10}^{15}$ for the reaction: $\mathrm{Cu}(s)+2{\mathrm{Ag}}^{+}(\mathrm{aq})\rightleftharpoons {\mathrm{Cu}}^{2+}(\mathrm{aq})+2\mathrm{Ag}(s)$ The equilibrium constant for the reaction $\frac{1}{2}{\mathrm{Cu}}^{2+}(\mathrm{aq})+\mathrm{Ag}(s)\rightleftharpoons \frac{1}{2}\mathrm{Cu}(s)+{\mathrm{Ag}}^{+}(\mathrm{aq})$ is $x\times {10}^{-8}$. The value of $x$ is ______. (Round off the answer to the nearest integer)
$2\mathrm{NOCl}(g)\rightleftharpoons 2\mathrm{NO}(g)+{\mathrm{Cl}}_{2}(g)$ In an experiment, $2.0$ moles of $\mathrm{NOCl}$ was placed in a one-litre flask and the concentration of $\mathrm{NO}$ after equilibrium established, was found to be $0.4\mathrm{mol}/L$. The equilibrium constant at $30^{\circ}C$ is_____$\times {10}^{-4}$.
A commercially sold conc. $\mathrm{HCl}$ is $35%\mathrm{HCl}$ by mass. If the density of this commercial acid is $1.46g/\mathrm{mL}$, the molarity of this solution is : (Atomic mass : $\mathrm{Cl}=35.5\mathrm{amu},H=1\mathrm{amu}$)
If the solubility product of $\mathrm{PbS}$ is $8\times {10}^{-28}$, then the solubility of $\mathrm{PbS}$ in pure water at $298K$ is $x\times {10}^{-16}\mathrm{mol}{L}^{-1}$. The value of $x$ is____ (Nearest integer) [Given $\sqrt{2}=1.41$]