JEE Main Chemistry — Physical Chemistry previous year questions with solutions.
Electricity is passed through an acidic solution of $\mathrm{Cu}^{2+}$ till all the $\mathrm{Cu}^{2+}$ was exhausted, leading to the deposition of 300 mg of Cu metal. However, a current of 600 mA was continued to pass through the same solution for another 28 minutes by keeping the total volume of the solution fixed at 200 mL. The total volume of oxygen evolved at STP during the entire process is $\_\_\_\_$ mL. (Nearest integer) [Given: $\mathrm{Cu}^{2+}(\mathrm{aq})+2 \mathrm{e}^{-} \rightarrow \mathrm{Cu}(\mathrm{s}) \mathrm{E}_{\text {red }}^{\mathrm{o}}=+0.34 \mathrm{~V}$ $\mathrm{O}_{2}(\mathrm{~g})+4 \mathrm{H}^{+}+4 \mathrm{e}^{-} \rightarrow 2 \mathrm{H}_{2} \mathrm{O} \mathrm{E}_{\text {red }}^{\mathrm{o}}=+1.23 \mathrm{~V}$ Molar mass of $\mathrm{Cu}=63.54 \mathrm{~g} \mathrm{~mol}^{-1}$ Molar mass of $\mathrm{O}_{2}=32 \mathrm{~g} \mathrm{~mol}^{-1}$ Faraday Constant $=96500 \mathrm{C} \mathrm{mol}^{-1}$ Molar volume at $\mathrm{STP}=22.4 \mathrm{~L}$]
Solution A is prepared by dissolving $1$ g of a protein (molar mass $= 50000$ g mol$^{-1}$) in $0.5$ L of water at $300$ K. Its osmotic pressure is $x$ bar. Solution B is made by dissolving $2$ g of same protein in $1$ L of water at $300$ K. Osmotic pressure of solution B is $y$ bar. Entire solution of A is mixed with entire solution of B at same temperature. The osmotic pressure of resultant solution is $z$ bar. $x, y$ and $z$ respectively are: $(R = 0.083$ L bar mol$^{-1}$ K$^{-1})$
An oxide of iron contains $69.9\%$ iron, its empirical formula, is: (Given: Molar mass of Fe and O are $56$ and $16$ g mol$^{-1}$ respectively.)
An organic compound undergoes first order decomposition. The time taken for decomposition to $\left(\frac{1}{8}\right)^{\text {th }}$ and $\left(\frac{1}{10}\right)^{\text {th }}$ of its initial concentration are $\mathrm{t}_{1 / 8}$ and $\mathrm{t}_{1 / 10}$ respectively. What is the value of $\frac{\mathrm{t}_{1 / 8}}{\mathrm{t}_{1 / 10}} \times 10$ ? ($\log 2=0.3$)
For a closed circuit Daniell cell, which of the following plots is the accurate one at a given temperature?
Match the LIST-I with LIST-II \(\begin{array}{|c|l|c|c|} \hline & \textbf{List-I (Thermodynamic Process)} & & \textbf{List-II} \\ & & & \textbf{(Magnitude in kJ)} \\ \hline A. & \begin{array}{l} \text{Work done in reversible,} \\ \text{isothermal expansion of }\\ \text{2 mol ideal gas from } 2\,\mathrm{dm}^3 \\ \text{ to } 20\,\mathrm{dm}^3 \text{ at } 300\,\mathrm{K} \end{array} & I. & 4 \\ \hline B. & \begin{array}{l} \text{Work done in irreversible} \\ \text{isothermal expansion of }\\ 1 \text{ mol ideal gas from } 1\,\mathrm{m}^3 \text{ to } 3\,\mathrm{m}^3 \\ \text{at } 300\,\mathrm{K} \text{ against} \\ \text{constant pressure } 3\,\mathrm{kPa} \end{array} & II. & 11.5 \\ \hline C. & \begin{array}{l} \text{Change in internal energy} \\ \text{for adiabatic expansion of }\\ 1 \text{ mol ideal gas, } \Delta T = 320\,\mathrm{K}, \; \\ \overline{C}_V=\dfrac{3}{2}R \end{array} & III. & 6 \\ \hline D. & \begin{array}{l} \text{Change in enthalpy at constant} \\ \text{pressure of }\\ 1 \text{ mol ideal gas, } \Delta T = 337\,\mathrm{K}, \; \\ \overline{C}_p=\dfrac{5}{2}R \end{array} & IV. & 7 \\ \hline \end{array}\) Choose the correct answer from the options given below:
For a reaction $A \rightarrow P$ at $T\text{ K}$, the half life $(t_{1/2})$ is plotted as a function of initial concentration $[A]_0$ of $A$ as given below.  The value of $x$ in the given figure is _______ s (Nearest integer)
How many grams of residue is obtained by heating $2.76$ g of silver carbonate?<br>(Given: Molar mass of C, O and Ag are $12$, $16$ and $108$ g mol$^{-1}$ respectively)
Consider the following two half-cell reactions along with the standard reduction potential given: $CO_2 + 6H^+ + 6e^- \rightarrow CH_3 OH + H_2 O \quad E°_{red} = 0.02$ V $\dfrac{1}{2} O_2 + 2H^+ + 2e^- \rightarrow H_2 O \quad E°_{red} = 1.23$ V A fuel cell was set up using the above two reactions such that the cell operates under the standard condition of $1$ bar pressure and $298$ K temperature. The fuel cell works with $80\%$ efficiency. If the work derived from the cell using $1$ mol of $CH_3 OH$ is used to compress an ideal gas isothermally against a constant pressure of $1$ kPa, then the change in the volume of the gas, $\Delta V = $ _____ m$^3$. (nearest integer) Given: $F = 96500$ C mol$^{-1}$
The pH of a solution obtained by mixing $5$ mL of $0.1$ M $NH_4OH$ solution with $250$ mL of $0.1$ M $NH_4Cl$ solution is _____ $\times 10^{-2}$. (Nearest integer) Given: $pK_b(NH_4OH) = 4.74$ $\log 2 = 0.30$ $\log 3 = 0.48$ $\log 5 = 0.70$
$\mathrm{A}+2 \mathrm{~B} \longrightarrow \mathrm{AB}_{2}$<br>36.0 g of 'A' (Molar mass: $60 \mathrm{~g} \mathrm{~mol}^{-1}$) and 56.0 g of ' $\mathrm{B}^{\prime}$ (Molar mass: $80 \mathrm{~g} \mathrm{~mol}^{-1}$) are allowed to react. Which of the following statements are correct ?<br>A. 'A' is the limiting reagent.<br>B. $77.0 \mathrm{~g}$ of $\mathrm{AB}_{2}$ is formed.<br>C. Molar mass of $A B_{2}$ is $140 \mathrm{~g} \mathrm{~mol}^{-1}$.<br>D. $15.0 \mathrm{~g}$ of A is left unreacted after the completion of reaction.<br>Choose the correct answer from the options given below :
Match the LIST-I with LIST-II <table class="pyq-table"><tbody><tr><th>List-I Orbital</th><th>List-II Radial nodes and nodal plane</th></tr><tr><td>A. $2s$</td><td>I. $1$ Radial node + two nodal planes</td></tr><tr><td>B. $3s$</td><td>II. $1$ Radial node + one nodal plane</td></tr><tr><td>C. $3p$</td><td>III. $2$ Radial nodes + No nodal plane</td></tr><tr><td>D. $4d$</td><td>IV. $1$ Radial node + No nodal plane</td></tr></tbody></table> Choose the correct answer from the options given below:
The correct order of total number of atoms present in (A) $2$ moles of cyclohexane (B) $684$ g of sucrose (C) $90.8$ L of dihydrogen at STP is:
Two liquids A and B form an ideal solution. At 320 K, the vapour pressure of the solution, containing 3 mol of A and 1 mol of B is 500 mm Hg. At the same temperature, if 1 mol of A is further added to this solution, vapour pressure of the solution increases by 20 mm Hg. Vapour pressure (in mm Hg) of B in pure state is $\_\_\_\_$. (Nearest integer)
For a general redox reaction Anode : $\text{Red}_1 \rightarrow \text{Ox}_1^{n_1^+} + n_1 e^-$ Cathode : $\text{Ox}_2 + n_2 e^- \rightarrow \text{Red}_2^{n_2^-}$ Which of the following statement is incorrect ?
Given below are two statements : Statement (I) : 1,2,3-Trihydroxypropane can be separated from water by simple distillation. Statement (II) : An azeotropic mixture cannot be separated by fractional distillation. In the light of the above statements, choose the correct answer from the options given below :
' W ' g of a non-volatile electrolyte solid solute of molar mass ' M ' $\mathrm{g} \mathrm{mol}^{-1}$ when dissolved in 100 mL water, decreases vapour pressure of water from 640 mm Hg to 600 mm Hg. If aqueous solution of the electrolyte boils at 375 K and $\mathrm{K}_{\mathrm{b}}$ for water is $0.52 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$, then the mole fraction of the electrolyte solute $\left(x_{2}\right)$ in the solution can be expressed as (Given : density of water $=1 \mathrm{~g} / \mathrm{mL}$ and boiling point of water $=373 \mathrm{~K}$)
Match List - I with List - II. Given $V_1$ and $V_2$ are initial and final volumes respectively.<table class="pyq-table"><tbody><tr><th>List - I (Isothermal process)</th><th>List - II (Expression)</th></tr><tr><td>A. Reversible expansion</td><td>I. $q = 0$</td></tr><tr><td>B. Free expansion</td><td>II. $q = nRT \ln\dfrac{V_2}{V_1}$</td></tr><tr><td>C. Irreversible Compression</td><td>III. $w = -p_{ext}(V_1 - V_2)$</td></tr><tr><td>D. Cyclic reversible</td><td>IV. $\dfrac{q_{rev}}{T} = 0$</td></tr></tbody></table>Choose the correct answer from the options given below :
In the reaction, $2 \mathrm{Al}(\mathrm{s})+6 \mathrm{HCl}(\mathrm{aq}) \rightarrow 2 \mathrm{Al}^{3+}(\mathrm{aq})+6 \mathrm{Cl}^{-}(\mathrm{aq})+3 \mathrm{H}_{2}(\mathrm{~g})$
At $27^{\circ} \mathrm{C}$ in presence of a catalyst, activation energy of a reaction is lowered by $10 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The logarithm of ratio of $\frac{\mathrm{k} \text { (catalysed) }}{\mathrm{k} \text { (uncatalysed) }}$ is.... (Consider that the frequency factor for both the reactions is same)
What volume of hydrogen gas at STP would be liberated by action of $50\text{ mL}$ of $H_2SO_4$ of $50\%$ purity (density $= 1.3\text{ g mL}^{-1}$) on $20\text{ g}$ of zinc ? Given : Molar mass of H, O, S, Zn are $1, 16, 32, 65\text{ g mol}^{-1}$ respectively.
Observe the following equilibrium in a 1 L flask. $\mathrm{A}(\mathrm{~g}) \rightleftharpoons \mathrm{B}(\mathrm{~g})$ At $\mathrm{T}(\mathrm{K})$, the equilibrium concentrations of A and B are 0.5 M and 0.375 M respectively. 0.1 moles of A is added into the flask and heated to $\mathrm{T}(\mathrm{K})$ to establish the equilibrium again. The new equilibrium concentrations (in M) of A and B are respectively
The pH of a 0.01 M NaOH solution at 25°C is:
Which of the following contain the same number of atoms ? (Given : Molar mass in g mol$^{-1}$ of H, He, O and S are $1, 4, 16$ and $32$ respectively) A. $2$ g of O$_2$ gas B. $4$ g of SO$_2$ gas C. $1400$ mL of O$_2$ at STP D. $0.05$ L of He at STP E. $0.0625$ mol of H$_2$ gas Choose the correct answer from the options given below :