Physical Chemistry PYQ — Page 2

First order gas phase reaction $A \rightarrow B + C$ $p_i =$ initial pressure of gas A, $p_t =$ total pressure of the reaction mixture at time $t$ Expression of rate constant ($k$) is

Which of the following mixture gives a buffer solution with $\mathrm{pH}=9.25$ ? Given : $\mathrm{pK}_{\mathrm{b}}\left(\mathrm{NH}_{4} \mathrm{OH}\right)=4.75$

Aqueous HCl reacts with $\mathrm{MnO}_{2}(\mathrm{~s})$ to form $\mathrm{MnCl}_{2}(\mathrm{aq}), \mathrm{Cl}_{2}(\mathrm{~g})$ and $\mathrm{H}_{2} \mathrm{O}(l)$. What is the weight (in g) of $\mathrm{Cl}_{2}$ liberated when 8.7 g of $\mathrm{MnO}_{2}(\mathrm{~s})$ is reacted with excess aqueous HCl solution? (Given Molar mass in $\mathrm{g} \mathrm{mol}^{-1} \mathrm{Mn}=55, \mathrm{Cl}=35.5, \mathrm{O}=16, \mathrm{H}=1$)

In order to oxidise a mixture of $1$ mole each of $FeC_2O_4$, $Fe_2(C_2O_4)_3$, $FeSO_4$ and $Fe_2(SO_4)_3$ in acidic medium, the number of moles of $KMnO_4$ required is

The wavelength of spectral line obtained in the spectrum of $\mathrm{Li}^{2+}$ ion, when the transition takes place between two levels whose sum is 4 and difference is 2, is

The wave numbers of three spectral lines of H atom are considered. Identify the set of spectral lines belonging to Balmer series. ($\mathrm{R}=$ Rydberg constant)

The energy of first (lowest) Balmer line of H atom is $x \mathrm{~J}$. The energy (in J) of second Balmer line of H atom is :

At 298 K, the mole percentage of $\mathrm{N}_{2}(\mathrm{~g})$ in air is $80 \%$. Water is in equilibrium with air at a pressure of 10 atm. What is the mole fraction of $\mathrm{N}_{2}(\mathrm{~g})$ in water at 298 K ? ($\mathrm{K}_{\mathrm{H}}$ for $\mathrm{N}_{2}$ is $6.5 \times 10^{7} \mathrm{~mm} \mathrm{Hg}$)

For the following reaction at $50°$C and at $2$ atm pressure, $2N_2O_5(g) \rightleftharpoons 2N_2O_4(g)+O_2(g)$ $N_2O_5$ is $50\%$ dissociated. The magnitude of standard free energy change at this temperature is $x$. $x=$ ______ J mol$^{-1}$ [Nearest integer]. Given: $R=8.314$ J mol$^{-1}$ K$^{-1}$, $\log 2=0.30$, $\log 3=0.48$, $\ln 10=2.303$, $°C+273=K$

What is the mole fraction of water in $10$% by weight (w/w) of aqueous urea solution? [Given: Molar mass of H, O, C and N are $1$, $16$, $12$ and $14$ g mol$^{-1}$ respectively.]

Consider a weak base ' B ' of $\mathrm{pK}_{\mathrm{b}}=5.699$. ' $x$ ' mL of 0.02 M HCl and ' y ' mL of 0.02 M weak base ' B ' are mixed to make 100 mL of a buffer of pH 9 at $25^{\circ} \mathrm{C}$. The values of ' $x$ ' and ' $y$ ' respectively are: [Given: $\log 2=0.3010, \log 3=0.4771, \log 5=0.699$]

Which of the following is correct set of $4$ quantum numbers of $19^{th}$ electron in Chromium (Atomic number $= 24$) in accordance with Aufbau principle?

At $27°$C, $0.1$ M, $1$ L $K_4[Fe(CN)_6]$ aqueous solution and $0.1$ M, $1$ L $FeCl_3$ aqueous solution are placed in a container separated by a semi permeable membrane AB. Assume complete dissociation of both the solutes. Which of the following statement is correct? 

Consider the reaction $2\text{H}_2\text{S}(g) + 3\text{O}_2(g) \rightarrow 2\text{H}_2\text{O}(l) + 2\text{SO}_2(g)$ The magnitude of enthalpy change for the reaction in kJ mol$^{-1}$ is ________. (Nearest integer) Given: $\Delta_fH^{\ominus}(\text{H}_2\text{S}) = -20.1$ kJ mol$^{-1}$ $\Delta_fH^{\ominus}(\text{H}_2\text{O}) = -286.0$ kJ mol$^{-1}$ $\Delta_fH^{\ominus}(\text{SO}_2) = -297.0$ kJ mol$^{-1}$

Consider the reaction $X \rightleftharpoons Y$ at $300$ K. If $\Delta H^{\theta}$ and $K$ are $28.40$ kJ mol$^{-1}$ and $1.8 \times 10^{-7}$ at the same temperature, then the magnitude of $\Delta S^{\theta}$ for the reaction in J K$^{-1}$ mol$^{-1}$ is _______. (Nearest integer) (Given: $R = 8.3$ J K$^{-1}$ mol$^{-1}$, $\ln 10 = 2.3$, $\log 3 = 0.48$, $\log 2 = 0.30$)

If the enthalpy of sublimation of Li is $155 \mathrm{~kJ} \mathrm{~mol}^{-1}$, enthalpy of dissociation of $\mathrm{F}_{2}$ is $150 \mathrm{~kJ} \mathrm{~mol}^{-1}$, ionization enthalpy of Li is $520 \mathrm{~kJ} \mathrm{~mol}^{-1}$, electron gain enthalpy of F is $-313 \mathrm{~kJ} \mathrm{~mol}^{-1}$, standard enthalpy of formation of LiF is $-594 \mathrm{~kJ} \mathrm{~mol}^{-1}$. The magnitude of lattice enthalpy of LiF is $\_\_\_\_$ $\mathrm{kJ} \mathrm{mol}^{-1}$. (Nearest Integer)

Use the following data : \(\begin{array}{|c|c|c|} \hline \text {Substance } & \frac{\Delta_f \mathrm{H}^{\ominus}(500 \mathrm{~K})}{\mathrm{kJmol}^{-1}} & \frac{\mathrm{~S}^{\ominus}(500 \mathrm{~K})}{\mathrm{JK}^{-1} \mathrm{~mol}^{-1}} \\ \hline \mathrm{AB}(\mathrm{~g}) & 32 & 222 \\ \hline \mathrm{~A}_2(\mathrm{g}) & 6 & 146 \\ \hline \mathrm{~B}_2(\mathrm{g}) & x & 280 \\ \hline \end{array}\) One mole each of $\mathrm{A}_{2}(\mathrm{~g})$ and $\mathrm{B}_{2}(\mathrm{~g})$ are taken in a 1 L closed flask and allowed to establish the equilibrium at 500 K. $\mathrm{A}_{2}(\mathrm{~g})+\mathrm{B}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{AB}(\mathrm{~g})$ The value of $x\left(\mathrm{in} \mathrm{kJ} \mathrm{mol}^{-1}\right)$ is $\_\_\_\_$. (Nearest integer) (Given : $\log \mathrm{K}=2.2 \quad \mathrm{R}=8.3 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$)

Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and $\mathrm{PQ}_{2}$. When 1 g of PQ is dissolved in 50 g of solvent ${ }^{\prime} \mathrm{A}^{\prime}, \Delta \mathrm{T}_{\mathrm{b}}$ was 1.176 K while when 1 g of $\mathrm{PQ}_{2}$ is dissolved in 50 g of solvent ${ }^{\prime} \mathrm{A}^{\prime}, \Delta \mathrm{T}_{\mathrm{b}}$ was 0.689 K. ($\mathrm{K}_{\mathrm{b}}$ of ' $\mathrm{A}^{\prime}=5 \mathrm{~K} \mathrm{~kg} \mathrm{~mol}^{-1}$). The molar masses of elements P and Q (in $\mathrm{g} \mathrm{mol}^{-1}$) respectively, are :

Consider the reaction $aX \rightarrow bY$, for which the rate constant at $30°C$ is $1 \times 10^{-3}$ mol$^{-1}$ L s$^{-1}$. Which of the following statements are true? A. When concentration of 'X' is increased to four times, the rate of reaction becomes $16$ times. B. The reaction is a second order reaction. C. The half-life period is independent of the concentration of X. D. Decomposition of $N_2 O_5$ is an example of the above reaction. E. $\ln\dfrac{[R_o]}{[R]}$ vs time is valid for the above reaction. Choose the correct answer from the options given below:

The hydrogen spectrum consists of several spectral lines in Lyman series ($\mathrm{L}_{1}, \mathrm{~L}_{2}$, $\mathrm{L}_{3} \ldots ; \mathrm{L}_{1}$ has lowest energy among Lyman series). Similarly it consists of several spectral lines in Balmer series $\left(\mathrm{B}_{1}, \mathrm{~B}_{2}, \mathrm{~B}_{3} \ldots ; \mathrm{B}_{1}\right.$ has lowest energy among Balmer lines). The energy of $L_{1}$ is $x$ times the energy of $B_{1}$. The value of $x$ is $\_\_\_\_$ $\times 10^{-1}$ . (Nearest integer)

For the thermal decomposition of reactant $\mathrm{AB}(\mathrm{g})$, the following plot is constructed.  The half life of the reaction is ' $x^{\prime} \min$. $x=$ $\_\_\_\_$ min. (Nearest integer)

500 mL of 1.2 M KI solution is mixed with 500 mL of $0.2 \mathrm{M} \mathrm{KMnO}_{4}$ solution in basic medium. The liberated iodine was titrated with standard $0.1 \mathrm{M} \mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ solution in the presence of starch indicator till the blue color disappeared. The volume (in L) of $\mathrm{Na}_{2} \mathrm{~S}_{2} \mathrm{O}_{3}$ consumed is $\_\_\_\_$. (Nearest integer)

Arrange the following isothermal processes in order of the magnitude of the work ($p - V$) involved between states $1$ and $2$. A. Expansion in single stage $w_A$ B. Expansion in multi stages $w_B$ C. Compression in single stage $w_C$ D. Compression in multi stages $w_D$ Choose the correct option.

Match List-I with List-II.<table class="pyq-table"><tbody><tr><th>List-I Mass of substance</th><th>List-II Number of atoms</th></tr><tr><td>A. $1.8$ mg water</td><td>I. $2\times 10^{-4}\times N_A$</td></tr><tr><td>B. $9.8$ mg sulphuric acid</td><td>II. $1.5\times 10^{-4}\times N_A$</td></tr><tr><td>C. $1.8$ mg carbon</td><td>III. $3\times 10^{-4}\times N_A$</td></tr><tr><td>D. $5.85$ mg salt (NaCl)</td><td>IV. $7\times 10^{-4}\times N_A$</td></tr></tbody></table>Choose the correct answer from the options given below: