JEE Main Chemistry — Physical Chemistry previous year questions with solutions.
If wavelength of the first line of the Paschen series of hydrogen atom is $720\mathrm{nm}$, then the wavelength of the second line of this series is _______ $\mathrm{nm}$. (Nearest integer)
Enthalpies of formation of ${\mathrm{CCl}}_{4}(g),{H}_{2}O(g),{\mathrm{CO}}_{2}(g)$ and $\mathrm{HCl}$ are $-105,-242,-394$ and $-92\mathrm{kJ}{\mathrm{mol}}^{-1}$ respectively. The magnitude of enthalpy of the reaction given below is ${\mathrm{kJmol}}^{-1}$. (nearest integer) ${\mathrm{CCl}}_{4}(g)+2{H}_{2}O(g)\rightarrow {\mathrm{CO}}_{2}(g)+4\mathrm{HCl}(g)$
The specific conductance of $0.0025M$ acetic acid is $5\times {10}^{-5}S{\mathrm{cm}}^{-1}$ at a certain temperature. The dissociation constant of acetic acid is ___________ $\times {10}^{-7}$.(Nearest integer) Consider limiting molar conductivity of ${\mathrm{CH}}_{3}\mathrm{COOH}$ as $400S{\mathrm{cm}}^{2}{\mathrm{mol}}^{-1}$
${A}_{2}+{B}_{2}\rightarrow 2\mathrm{AB}.\Delta {H}_{f}=-200\mathrm{kJ}{\mathrm{mol}}^{-1}$ $\mathrm{AB},{A}_{2}$ and ${B}_{2}$ are diatomic molecules. If the bond enthalpies of ${A}_{2},{B}_{2}$ and $\mathrm{AB}$ are in the ratio$1:0.5:1,$ then the bond enthalpy of ${A}_{2}$ is$_________kJ{\mathrm{mol}}^{–1}$ (Nearest integer)
For a metal ion, the calculated magnetic moment is $4.90\mathrm{BM}$. This metal ion has _______ number of unpaired electrons
${\mathrm{KClO}}_{3}+6{\mathrm{FeSO}}_{4}+3{H}_{2}{\mathrm{SO}}_{4}\rightarrow \mathrm{KCl}+3{\mathrm{Fe}}_{2}({\mathrm{SO}}_{4}{)}_{3}+3{H}_{2}O$ The above reaction was studied at $300K$ by monitoring the concentration of ${\mathrm{FeSO}}_{4}$ in which initial concentration was $10M$ and after half an hour became $8.8M$. The rate of production of ${\mathrm{Fe}}_{2}({\mathrm{SO}}_{4}{)}_{3}$ is _______ $\times l{0}^{–6}\mathrm{mol}{L}^{–1}s{}^{–1}$ (Nearest integer)
Millimoles of calcium hydroxyide required to produce $100\mathrm{mL}$ of the aqueous solution of $\mathrm{pH}12$ is $x\times {10}^{-1}$. The value of $x$ is _____ (Nearest integer). Assume complete dissociation.
The energy of one mole of photons of radiation of frequency $2\times {10}^{12}\mathrm{Hz}$ in ${\mathrm{Jmol}}^{-1}$ is _____ . (Nearest integer) (Given: $h=6.626\times {10}^{-34}\mathrm{Js}$ ${N}_{A}=6.022\times {10}^{23}{\mathrm{mol}}^{-1}$)
If the boiling points of two solvents $X$ and $Y$ (having same molecular weights) are in the ratio $\text{2: 1}$ and their enthalpy of vaporizations are in the ratio $1:2$, then the boiling point elevation constant of $X$ is $m$ times the boiling point elevation constant of $Y$. The value of $m$ is (nearest integer).
Incorrect statement for the use of indicator in acid-base titration is:
A metal surface of $100{\mathrm{cm}}^{2}$ area has to be coated with nickel layer of thickness $0.001\mathrm{mm}.$ A current of $2A$ was passed through a solution of $\mathrm{Ni}{({\mathrm{NO}}_{3})}_{2}$ for $‘x’$ seconds to coat the desired layer. The value of $x$ is _________. (Nearest integer) ($\rho Ni$ (density of Nickel) is $10g{\mathrm{mL}}^{–1},$Molar mass of Nickel is $60g{\mathrm{mol}}^{-1}F=96500{\mathrm{Cmol}}^{-1}$)
$30.4\mathrm{kJ}$ of heat is required to melt one mole of sodium chloride and the entropy change at the melting point is $28.4J{K}^{–1}{\mathrm{mol}}^{–1}$ at $1\mathrm{atm}$. The melting point of sodium chloride is _______ $K$ (Nearest Integer)
When 2 litre of ideal gas expands isothermally into vacuum to a total volume of $6$ litre, the change in internal energy is _____ J. (Nearest integer)
Lead storage battery contains $38%$ by weight solution of ${H}_{2}{\mathrm{SO}}_{4}$. The van't Hoff factor is $2.67$ at this concentration. The temperature in Kelvin at which the solution in the battery will freeze is _____ (Nearest integer). Given ${K}_{f}=1.8K\mathrm{kg}{\mathrm{mol}}^{-1}$
$25\mathrm{mL}$ of an aqueous solution of $\mathrm{KCl}$ was found to require $20\mathrm{mL}$ of $1M{\mathrm{AgNO}}_{3}$ solution when titrated using ${K}_{2}{\mathrm{CrO}}_{4}$ as an indicator. What is the depression in freezing point of $\mathrm{KCl}$ solution of the given concentration? (Nearest integer). (Given : ${K}_{f}=2.0K\mathrm{kg}{\mathrm{mol}}^{-1}$ ) Assume 1) $100%$ ionization and 2) density of the aqueous solution as $1g{\mathrm{mL}}^{-1}$
The titration curve of weak acid vs. strong base with phenolphthalein as indicator is shown below. The ${K}_{\text{phenolphthalein }}=4\times {10}^{-10}$ Given: $\mathrm{log}2=0.3$  The number of following statement/s which is/are correct about phenolphthalein is _______ A. It can be used as an indicator for the titration of weak acid with weak base. B. It begins to change colour at $\mathrm{pH}=8.4$ C. It is a weak organic base D. It is colourless in acidic medium
The volume of $\mathrm{HCl}$, containing $73g{L}^{-1}$, required to completely neutralise $\mathrm{NaOH}$ obtained by reacting $0.69g$ of metallic sodium with water, is _____ $\mathrm{mL}$. (Nearest Integer) (Given : molar Masses of $\mathrm{Na},\mathrm{Cl},O,H$ are $23,35.5,16$ and $1g{\mathrm{mol}}^{-1}$ respectively)
$1$ mole of ideal gas is allowed to expand reversibly and adiabatically from a temperature of $27^{\circ}C$. The work done is $3\mathrm{kJ}{\mathrm{mol}}^{-1}$. The final temperature of the gas is _____ $K$ (Nearest integer). Given ${C}_{v}=20J{\mathrm{mol}}^{-1}{K}^{-1}$
When a $60W$ electric heater is immersed in a gas for $100s$ in a constant volume container with adiabatic walls, the temperature of the gas rises by $5^{\circ}C$. The heat capacity of the given gas is ${\mathrm{JK}}^{-1}$ (Nearest integer)
The shortest wavelength of hydrogen atom in Lyman series is $\lambda$. The longest wavelength in Balmer series of ${\mathrm{He}}^{+}$ is
The reaction $2\mathrm{NO}+{\mathrm{Br}}_{2}\rightarrow 2\mathrm{NOBr}$ takes place through the mechanism given below $\mathrm{NO}+{\mathrm{Br}}_{2}\overset{}{\rightleftharpoons }{\mathrm{NOBr}}_{2}(\mathrm{fast})$ ${\mathrm{NOBr}}_{2}+\mathrm{NO}\rightarrow 2\mathrm{NOBr}(\mathrm{slow})$ The overall order of the reaction is _____.
$20\mathrm{mL}$ of calcium hydroxide was consumed when it was reacted with $10\mathrm{mL}$ of unknown solution of ${H}_{2}{\mathrm{SO}}_{4}.$ Also $20\mathrm{mL}$ standard solution of $0.5M\mathrm{HCl}$ containing $2$ drops of phenolphthalein was titrated with calcium hydroxide, the mixture showed pink colour when burette displayed the value of $35.5\mathrm{mL}$ whereas the burette showed $25.5\mathrm{mL}$ initially. The concentration of ${H}_{2}{\mathrm{SO}}_{4}$ is $_______M.$ (Nearest integer)
The volume of hydrogen liberated at STP by treating $2.4g$ of magnesium with excess of hydrochloric acid is ......$\times {10}^{-2}L$. Given Molar volume of gas is $22.4L$ at STP. Molar mass of magnesium is $24g{\mathrm{mol}}^{-1}$
The pH of a 0.1 M HCl solution is: