JEE Main Chemistry — Physical Chemistry previous year questions with solutions.
At $363K$, the vapour pressure of $A$ is $21\mathrm{kPa}$ and that of $B$ is $18\mathrm{kPa}$. One mole of $A$ and $2$ moles of $B$ are mixed. Assuming that this solution is ideal, the vapour pressure of the mixture is___________ $\mathrm{kPa}$. $($Round of to the Nearest Integer$)$.
$15\mathrm{mL}$ of aqueous solution of ${\mathrm{Fe}}^{2+}$ in acidic medium completely reacted with $20\mathrm{mL}$ of $0.03M$ aqueous ${\mathrm{Cr}}_{2}{{O}_{7}}^{2-}.$ The molarity of the ${\mathrm{Fe}}^{2+}$ solution is _______ $\times {10}^{-2}M$ (Round off to the Nearest Integer).
When $10\mathrm{mL}$ of an aqueous solution of ${\mathrm{Fe}}^{2+}$ ions was titrated in the presence of dil ${H}_{2}{\mathrm{SO}}_{4}$ using diphenylamine indicator, $15\mathrm{mL}$ of $0.02M$ solution of ${K}_{2}{\mathrm{Cr}}_{2}{O}_{7}$ was required to get the end point. The molarity of the solution containing ${\mathrm{Fe}}^{2+}$ ions is $x\times {10}^{-2}M$. The value of $x$ is ______. (Nearest integer)
Given below are two statements: Statement I : Bohr's theory accounts for the stability and line spectrum of ${\mathrm{Li}}^{+}$ ion. Statement II : Bohr's theory was unable to explain the splitting of spectral lines in the presence of a magnetic field. In the light of the above statements, choose the most appropriate answer from the options given below:
When $35\mathrm{mL}$ of $0.15M$ lead nitrate solution is mixed with $20\mathrm{mL}$ of $0.12M$ chromic sulphate solution, ____________$\times {10}^{-5}$ moles of lead sulphate precipitate out. (Round off to the Nearest Integer).
According to Bohr's atomic theory: (A) Kinetic energy of electron is $\propto \frac{{Z}^{2}}{{n}^{2}}.$ (B) The product of velocity (v) of electron and principal quantum number $(n),'vn'\propto {Z}^{2}.$ (C) Frequency of revolution of electron in an orbit is $\propto \frac{{Z}^{3}}{{n}^{3}}.$ (D) Coulombic force of attraction on the electron is $\propto \frac{{Z}^{3}}{{n}^{4}}.$ Choose the most appropriate answer from the options given below:
Outermost electronic configuration of a group $13$ element, $E,$ is $4{s}^{2},4{p}^{1}.$ The electronic configuration of an element of p-block period-five placed diagonally to element, $E$ is:
The reaction $2A+{B}_{2}\rightarrow 2\mathrm{AB}$ is an elementary reaction. For a certain quantity of reactants, if the volume of the reaction vessel is reduced by a factor of $3,$ the rate of the reaction increases by a factor of _____ . (Round off to the Nearest Integer).
______grams of $3-$Hydroxy propanal $(\mathrm{MW}=74)$ must be dehydrated to produce $7.8g$ of acrolein $(\mathrm{MW}=56)({C}_{3}{H}_{4}O)$ if the percentage yield is $64.$ (Round off to the Nearest Integer). $[\text{Given: Atomic masses}:C:12.0u,H:1.0u,O:16.0u]$
In polythionic acid, ${H}_{2}{S}_{x}{O}_{6}(x=3$ to $5$) the oxidation state(s) of sulphur is/are:
Sulphurous acid $({H}_{2}{\mathrm{SO}}_{3})$ has ${\mathrm{Ka}}_{1}=1.7\times {10}^{-2}$ and ${\mathrm{Ka}}_{2}=6.4\times {10}^{-8}.$ The $\mathrm{pH}$ of $0.588M{H}_{2}{\mathrm{SO}}_{3}$ is____________ $($Round off to the Nearest Integer$)$.
A source of monochromatic radiation wavelength $400\mathrm{nm}$ provides $1000J$ of energy in $10$ seconds. When this radiation falls on the surface of sodium, $x\times {10}^{20}$ electrons are ejected per second. Assume that wavelength $400\mathrm{nm}$ is sufficient for ejection of electron from the surface of sodium metal. The value of $x$ is ______. (Nearest integer) $(h=6.626\times {10}^{-34}\mathrm{Js})$
For a first order reaction, the ratio of the time for $75%$ completion of a reaction to the time for $50%$ completion is ___________ . (Integer answer)
An aqueous $\mathrm{KCl}$ solution of density $1.20g{\mathrm{mL}}^{-1}$ has a molality of $3.30\mathrm{mol}{\mathrm{kg}}^{-1}$. The molarity of the solution in ${\mathrm{molL}}^{-1}$ is____.(The Nearest integer) $[$Molar mass of $\mathrm{KCl}=74.5g]$
Data given for the following reaction is as follows : ${\mathrm{FeO}}_{(s)}+{C}_{(\mathrm{graphite})}\longrightarrow {\mathrm{Fe}}_{(s)}+{\mathrm{CO}}_{(g)}$ <table class="pyq-table"><tbody><tr><td>Substance</td><td>${\Delta }_{f}H^{\circ}({\mathrm{kJmol}}^{-1})$</td><td>$\Delta S^{\circ}({\mathrm{Jmol}}^{-1}{K}^{-1})$</td></tr><tr><td>${\mathrm{FeO}}_{(s)}$</td><td>$-266.3$</td><td>$57.49$</td></tr><tr><td>${C}_{(\mathrm{graphite})}$</td><td>$0$</td><td>$5.74$</td></tr><tr><td>${\mathrm{Fe}}_{(s)}$</td><td>$0$</td><td>$27.28$</td></tr><tr><td>${\mathrm{CO}}_{(g)}$</td><td>$-110.5$</td><td>$197.6$</td></tr></tbody></table>The minimum temperature in $K$ at which the reaction becomes spontaneous is_____.(Integer answer)
If the activation energy of a reaction is $80.9\mathrm{kJ}{\mathrm{mol}}^{-1}$, the fraction of molecules at $700K$, having enough energy to react to form products is ${e}^{-x}$. The value of $x$ is (Rounded off to the nearest integer) [Use $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1}$]
The formula of a gaseous hydrocarbon which requires 6 times of its own volume of ${O}_{2}$ for complete oxidation and produces $4$ times its own volume of ${\mathrm{CO}}_{2}$ is ${C}_{x}{H}_{y}.$ The value of $y$ is ________.
The reaction of cyanamide, ${\mathrm{NH}}_{2}{\mathrm{CN}}_{(s)}$ with oxygen was run in a bomb calorimeter and $\Delta U$ was found to be $-742.24\mathrm{kJ}{\mathrm{mol}}^{-1}$ . The magnitude of ${\Delta H}_{298}$ for the reaction ${\mathrm{NH}}_{2}{\mathrm{CN}}_{(s)}+\frac{3}{2}{O}_{2(g)}\rightarrow {N}_{2(g)}+{O}_{2(g)}+{H}_{2}{O}_{(l)}$ is $\mathrm{kJ}$. (Rounded off to the nearest integer) [Assume ideal gases and $R=8.314J{\mathrm{mol}}^{-1}{K}^{-1}$]
When $9.45g$ of ${\mathrm{ClCH}}_{2}\mathrm{COOH}$ is added to $500\mathrm{mL}$ of water, its freezing point drops by $0.5^{\circ}C.$ The dissociation constant of ${\mathrm{ClCH}}_{2}\mathrm{COOH}$ is $x\times {10}^{-3}.$ The value of $x$ is off to the nearest integer) $[{K}_{f({H}_{2}O)}=1.86K\mathrm{kg}{\mathrm{mol}}^{-1}]$
When $400\mathrm{mL}$ of $0.2M{H}_{2}{\mathrm{SO}}_{4}$ solution is mixed with $600\mathrm{mL}$ of $0.1\mathrm{MNaOH}$ solution, the increase in temperature of the final solution is $—\times {10}^{-2}K$. (Round off to the nearest integer). [Use :${H}^{+}(\mathrm{aq})+{\mathrm{OH}}^{-}(\mathrm{aq})\rightarrow {H}_{2}O:$${\Delta }_{\gamma }H=-57.1\mathrm{kJ}{\mathrm{mol}}^{-1}]$ Specific heat of ${H}_{2}O=4.18J{K}^{-1}{g}^{-1}$ , density of ${H}_{2}O=1.0g{\mathrm{cm}}^{-3}$ Assume no change in volume of solution on mixing.
${A}_{3}{B}_{2}$ is a sparingly soluble salt of molar mass $M(g{\mathrm{mol}}^{-1})$ and solubility $xg{L}^{-1}.$ The solubility product satisfies ${K}_{\mathrm{sp}}=a{(\frac{x}{M})}^{5}.$ The value of $a$ is __________ . (Integer answer)
${C}_{6}{H}_{6}$ freezes at $5.5^{\circ}C.$ The temperature at which a solution of $10g$ of ${C}_{4}{H}_{10}$ in $200g$ of ${C}_{6}{H}_{6}$ freeze is _______$C\circ .$ (nearest integer value), (The molal freezing point depression constant of ${C}_{6}{H}_{6}$ is $5.12^{\circ}C/m.$)
$2{\mathrm{SO}}_{2}(g)+{O}_{2}(g)\rightarrow 2{\mathrm{SO}}_{3}(g)$ The above reaction is carried out in a vessel starting with partial pressure ${P}_{{\mathrm{SO}}_{2}}=250m\mathrm{bar}$, ${P}_{{O}_{2}}=750m\mathrm{bar}$ and ${P}_{{\mathrm{SO}}_{3}}=0\mathrm{bar}$. When the reaction is complete, the total pressure in the reaction vessel is _____ $m\mathrm{bar}$. (Round off of the nearest integer).
A $6.50$ molal solution of $\mathrm{KOH}(\mathrm{aq}.)$ has a density of $1.89g{\mathrm{cm}}^{-3}$. The molarity of the solution is $\mathrm{mol}{\mathrm{dm}}^{-3}$. (Round off to the Nearest Integer). [Atomic masses: $K:39.0u;O:16.0u;H:1.0u$]