JEE Main Chemistry — Physical Chemistry previous year questions with solutions.
The reaction $\mathrm{X} \rightarrow \mathrm{Y}$ is an exothermic reaction. Activation energy of the reaction for $\mathrm{X}$ into $\mathrm{Y}$ is $150 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Enthalpy of reaction is $135 \mathrm{~kJ}$ $\mathrm{mol}^{-1}$. The activation energy for the reverse reaction, $\mathrm{Y} \rightarrow \mathrm{X}$ will be :
A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of $3 7 . {0}^{\circ } \text{C}$. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be (R = 8.314 J/mol K) (ln7.5 = 2.01)
The instantaneous rate of disappearance of $\mathrm{MnO}_4^{-}$ion in the following reaction is $4.56 \times 10^{-3} \mathrm{Ms}^{-1}$ $2 \mathrm{MnO}_4^{-}+10 \mathrm{I}^{-}+16 \mathrm{H}^{+} \rightarrow 2 \mathrm{Mn}^{2+}+5 \mathrm{I}_2+8 \mathrm{H}_2 \mathrm{O}$ The rate of appearance $\mathrm{I}_2$ is :
Vapour pressure of pure benzene is 119 torr and that of toluene is $37.0$ torr at the same temperature. Mole fraction of toluene in vapour phase which is in equilibrium with a solution of benzene and toluene having a mole fraction of toluene $0.50$, will be :
Which of the following statements/relationships is not correct in thermodynamic changes ?
In which of the following exothermic reactions, the heat liberated per mole is the highest ?
The incorrect expression among the following is :
A battery is constructed of $\mathrm{Cr}$ and $\mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7$. The unbalanced chemical equation when such a battery discharges is following: $$ \mathrm{Na}_2 \mathrm{Cr}_2 \mathrm{O}_7+\mathrm{Cr}+\mathrm{H}^{+} \rightarrow \mathrm{Cr}^{3+}+\mathrm{H}_2 \mathrm{O}+\mathrm{Na}^{+} $$ If one Faraday of electricity is passed through the battery during the charging, the number of moles of $\mathrm{Cr}^{3+}$ removed from the solution is
The ratio of number of oxygen atoms $(\mathrm{O})$ in $16.0 \mathrm{~g}$ ozone $\left(\mathrm{O}_3\right), 28.0 \mathrm{~g}$ carbon monoxide $(\mathrm{CO})$ and $16.0$ oxygen $\left(\mathrm{O}_2\right)$ is (Atomic mass : $\mathrm{C}=12, \mathrm{O}=16$ and Avogadro's constant $\mathrm{N}_{\mathrm{A}}=6.0 \times 10^{23} \mathrm{~mol}^{-1}$ )
The increasing order of the ionic radii of the given isoelectronic species is :
The entropy of a sample of a certain substance increases by $0.836 \mathrm{~J} \mathrm{~K}^{-1}$ on adding reversibly $0.3344 \mathrm{~J}$ of heat at constant temperature. The temperature of the sample is:
The solubility of $\mathrm{PbI}_2$ at $25^{\circ} \mathrm{C}$ is $0.7 \mathrm{~g} \mathrm{~L}^{-1}$. The solubility product of $\mathrm{PbI}_2$ at this temperature is (molar mass of $\mathrm{PbI}_2=461.2 \mathrm{~g} \mathrm{~mol}^{-1}$ )
An aqueous solution of oxalic acid dihydrate contains its $6.3 \mathrm{~g}$ in $250 \mathrm{ml}$. The volume of $0.1 \mathrm{~N}$ $\mathrm{NaOH}$ required to completely neutralize $10 \mathrm{ml}$ of this solution
Which of the following paramagnetic ions would exhibit a magnetic moment (spin only) of the order of $5 \mathrm{BM}$ ? (At. Nos. $\mathrm{Mn}=25, \mathrm{Cr}=24, \mathrm{~V}=23, \mathrm{Ti}=22$ )
A solution containing $0.85 \mathrm{~g}$ of $\mathrm{ZnCl}_2$ in $125.0 \mathrm{~g}$ of water freezes at $-0.23^{\circ} \mathrm{C}$. The apparent degree of dissociation of the salt is $\left(K_f\right.$ for water $=1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$, atomic mass: $\mathrm{Zn}=65.3$ and $\mathrm{Cl}=35.5)$
If the kinetic energy of an electron is increased four times, the wavelength of the de-Broglie wave associated with it would become
The enthalpy of neutralisation of $\mathrm{NH}_4 \mathrm{OH}$ with $\mathrm{HCl}$ is $-51.46 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and the enthalpy of neutralisation of $\mathrm{NaOH}$ with $\mathrm{HCl}$ is $-55.90 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The enthalpy of ionisation of $\mathrm{NH}_4 \mathrm{OH}$ is
$\mathrm{K}_{\mathrm{f}}$ for water is $1.86 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$. If your automobile radiator holds $1.0 \mathrm{~kg}$ of water, how many grams of ethylene glycol $\left(\mathrm{C}_2 \mathrm{H}_6 \mathrm{O}_2\right)$ must you add to get the freezing point of the solution lowered to $-2.8^{\circ} \mathrm{C}$ ?
The solubility (in mol $\mathrm{L}^{-1}$ ) of $\mathrm{AgCl}$ $\left(K_{\mathrm{sp}}=1.0 \times 10^{-10}\right)$ in a $0.1 \mathrm{M} \mathrm{KCl}$ solution will be
The difference between the reaction enthalpy change $\left(\Delta_{\mathrm{r}} \mathrm{H}\right)$ and reaction internal energy change $\left(\Delta_{\mathrm{r}} \mathrm{U}\right)$ for the reaction: $$ 2 \mathrm{C}_6 \mathrm{H}_6(\mathrm{l})+15 \mathrm{O}_2(\mathrm{~g}) \longrightarrow $$ at $300 \mathrm{~K}$ is $\left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\right)$
In the following balanced reaction,  values of $X, Y$ and $Z$ respectively are
$8 \mathrm{~mol}$ of $A B_3(\mathrm{~g})$ are introduced into a $1.0 \mathrm{dm}^3$ vessel. If it dissociates as $2 \mathrm{AB}_3(g) \rightleftharpoons A_2(g)+3 B_2(g)$. At equilibrium, $2 \mathrm{~mol}$ of $A_2$ are found to be present. The equilibrium constant of this reaction is
The equilibrium constant $\left(\mathrm{K}_{\mathrm{c}}\right)$ for the reaction $\mathrm{N}_2(\mathrm{g})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{NO}(\mathrm{g})$ at temperature $\mathrm{T}$ is $4 \times 10^{-4}$. The value of $\mathrm{K}_{\mathrm{c}}$ for the reaction, $\mathrm{NO}(\mathrm{g}) \rightarrow{1 / 2} \mathrm{~N}_2(\mathrm{g})+{1 / 2} \mathrm{~O}_2(\mathrm{g})$ at the same temperature is :
If the radius of first orbit of $\mathrm{H}$ atom is $a_0$, the deBroglie wavelength of an electron in the third orbit is