Physical Chemistry PYQ — Page 19

Given below are two statements : Statement (I) : A Buffer solution is the mixture of a salt and an acid or a base mixed in any particular quantities. Statement (II) : Blood is naturally occurring buffer solution whose \(\mathrm{pH}\) is maintained by \(\mathrm{H}_2 \mathrm{CO}_3 / \mathrm{HCO}_3^- \Theta\) concentrations. In the light of the above statements, choose the correct answer from the options given below :

Given below are two statements : Statement (I) : Aqueous solution of ammonium carbonate is basic. Statement (II) : Acidic/basic nature of salt solution of a salt of weak acid and weak base depends on ${K}_{a}$ and ${K}_{b}$ value of acid and the base forming it. In the light of the above statements, choose the most appropriate answer from the options given below :

The $\mathrm{pH}$ at which $\mathrm{Mg}(\mathrm{OH}{)}_{2}[{K}_{\mathrm{sp}}=1\times {10}^{-11}]$ begins to precipitate from a solution containing $0.10M$ ${\mathrm{Mg}}^{2+}$ ions is ______.

What happens to freezing point of benzene when small quantity of napthalene is added to benzene?

Consider the following single step reaction in gas phase at constant temperature. \(2 \mathrm{~A}_{(\mathrm{g})}+\mathrm{B}_{(\mathrm{g})} \rightarrow \mathrm{C}_{(\mathrm{g})}\) The initial rate of the reaction is recorded as \(\mathrm{r}_1\) when the reaction starts with \(1.5 \mathrm{~atm}\) pressure of \(\mathrm{A}\) and \(0.7 \mathrm{~atm}\) pressure of \(\mathrm{B}\). After some time, the rate \(\mathrm{r}_2\) is recorded when the pressure of \(\mathrm{C}\) becomes \(0.5 \mathrm{~atm}\). The ratio \(\mathrm{r}_1: \mathrm{r}_2\) is ______ \(\times 10^{-1}\). (Nearest integer)

Time required for \(99.9 \%\) completion of a first order reaction is _______ times the time required for completion of \(90 \%\) reaction.(nearest integer)

Given below are two statements : Statement I: The rate law for the reaction \(A+B \rightarrow C\) is rate \((r)=k[A]^2[B]\). When the concentration of both A and B is doubled, the reaction rate is increased " \(x\) " times. Statement II :  The figure is showing "the variation in concentration against time plot" for a " \(y\) " order reaction. The Value of \(x+y\) is ______

Consider the following reaction, the rate expression of which is given below \[ \begin{aligned} & \mathrm{A}+\mathrm{B} \rightarrow \mathrm{C} \\ & \text { rate }=\mathrm{k}[\mathrm{A}]^{1 / 2}[\mathrm{~B}]^{1 / 2} \end{aligned} \] The reaction is initiated by taking \(1 \mathrm{M}\) concentration of \(\mathrm{A}\) and \(\mathrm{B}\) each. If the rate constant \((\mathrm{k})\) is \(4.6 \times 10^{-2} \mathrm{~s}^{-1}\), then the time taken for \(\mathrm{A}\) to become \(0.1 \mathrm{M}\) is ______ sec. (nearest integer)

For a reaction taking place in three steps at same temperature, overall rate constant $K=\frac{{K}_{1}{K}_{2}}{{K}_{3}}$. If ${\mathrm{Ea}}_{1},{\mathrm{Ea}}_{2}$ and ${\mathrm{Ea}}_{3}$ are $40,50$ and $60\mathrm{kJ}/\mathrm{mol}$ respectively, the overall $\mathrm{Ea}$ is _________ $\mathrm{kJ}/\mathrm{mol}$.

When \(\Delta \mathrm{H}_{\mathrm{vap}}=30 \mathrm{~kJ} / \mathrm{mol}\) and \(\Delta \mathrm{S}_{\mathrm{vap}}=75 \mathrm{~J} \mathrm{~mol}^{-1} \mathrm{~K}^{-1}\), then the temperature of vapour, at one atmosphere is ______ \(\mathrm{K}\).

How can an electrochemical cell be converted into an electrolytic cell?

Match List - I with List - II. \(\begin{array}{ll} \text{List - I} & \text{List - II} \\ \text{Reaction} & \text{Type of redox reaction} \\ \text{(A) } \mathrm{N}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})} \rightarrow 2 \mathrm{NO}_{(\mathrm{g})} & \text{(I) Decomposition} \\ \text{(B) } 2 \mathrm{~Pb}\left(\mathrm{NO}_3\right)_{2(\mathrm{~s})} \rightarrow 2 \mathrm{PbO}_{(\mathrm{s})}+4 \mathrm{NO}_{2(\mathrm{~g})}+\mathrm{O}_{2(\mathrm{~g})} & \text{(II) Displacement} \\ \text{(C) } 2 \mathrm{Na}_{(\mathrm{s})}+2 \mathrm{H}_2 \mathrm{O}_{\text {(I) }} \rightarrow 2 \mathrm{NaOH}_{(\text {aq. }}+\mathrm{H}_{2(\mathrm{~g})} & \text{(III) Disproportionation} \\ \text{(D) } 2 \mathrm{NO}_{2(\text { g })}+2^{-} \mathrm{OH}( aq. ) \rightarrow \mathrm{NO}_{2(\text { aq. })}^{-}+\mathrm{NO}_{3(\text { aq. })}^{-}+\mathrm{H}_2 \mathrm{O}_{(\mathrm{l})} & \text{(IV) Combination} \end{array}\) Choose the correct answer from the options given below :

The four quantum numbers for the electron in the outer most orbital of potassium (atomic no. $19$) are

$0.05\mathrm{cm}$ thick coating of silver is deposited on a plate of $0.05{m}^{2}$ area. The number of silver atoms deposited on plate are _______$\times {10}^{23}$. (At mass Ag $=108,d=7.9g{\mathrm{cm}}^{-3})$ Round off to the nearest integer.

Match List I with List II \(\begin{array}{|l|l|l|l|} \hline & \text{ List - I (Element) } & & \text{List - II (Electronic configuration)} \\ \hline \text { A. } & \mathrm{N} & \text { I. } & {[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^2 4 \mathrm{p}^5 \mathrm{AR}} \\ \hline \text { B. } & \mathrm{S} & \text { II. } & {[\mathrm{Ne}] 3 \mathrm{~s}^2 3 \mathrm{p}^4} \\ \hline \text { C. } & \mathrm{Br} & \text { III. } & {[\mathrm{He}] 2 \mathrm{~s}^2 2 \mathrm{p}^3} \\ \hline \text { D. } & \mathrm{Kr} & \text { IV. } & {[\mathrm{Ar}] 3 \mathrm{~d}^{10} 4 \mathrm{~s}^2 4 \mathrm{p}^6} \\ \hline \end{array}\) Choose the correct answer from the options given below:

Reduction potential of ions are given below: ${\mathrm{ClO}}_{4}^{-}{\mathrm{IO}}_{4}^{-}{\mathrm{BrO}}_{4}^{-}$ $E^{\circ}=1.19V;E^{\circ}=1.65V;E^{\circ}=1.74V$ The correct order of their oxidising power is:

Compare the energies of following sets of quantum numbers for multielectron system. (A) \(\mathrm{n}=4,1=1\) (B) \(\mathrm{n}=4, \mathrm{l}=2\) (C) \(\mathrm{n}=3,1=1\) (D) \(\mathrm{n}=3,1=2\) (E) \(\mathrm{n}=4,1=0\) Choose the correct answer from the options given below :

For a sparingly soluble salt \(\mathrm{AB}_2\), the equilibrium concentrations of \(\mathrm{A}^{2+}\) ions and \(B^{-}\)ions are \(1.2 \times 10^{-4} \mathrm{M}\) and \(0.24 \times 10^{-3} \mathrm{M}\), respectively. The solubility product of \(\mathrm{AB}_2\) is :

The heat of combustion of solid benzoic acid at constant volume is \(-321.30 \mathrm{~kJ}\) at \(27^{\circ} \mathrm{C}\). The heat of combustion at constant pressure is \((-321.30-x \mathrm{R}) \mathrm{kJ}\), the value of \(x\) is _______.

Given below are two statements: Statement I : Gallium is used in the manufacturing of thermometers. Statement II : A thermometer containing gallium is useful for measuring the freezing point \((256 \mathrm{~K})\) of brine solution. In the light of the above statements, choose the correct answer from the options given below :

The density of ' \(x\) ' \(\mathrm{M}\) solution (' \(X\) ' molar) of \(\mathrm{NaOH}\) is \(1.12 \mathrm{~g} \mathrm{~mL}^{-1}\), while in molality, the concentration of the solution is \(3 \mathrm{~m}(3 \mathrm{molal})\). Then \(x\) is (Given : Molar mass of \(\mathrm{NaOH}\) is \(40 \mathrm{~g} / \mathrm{mol}\) )

Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R) Assertion (A) : Enthalpy of neutralisation of strong monobasic acid with strong monoacidic base is always \(-57 \mathrm{~kJ} \mathrm{~mol}^{-1}\). Reason (R) : Enthalpy of neutralisation is the amount of heat liberated when one mole of \(\mathrm{H}^{+}\) ions furnished by acid combine with one mole of \(\mathrm{OH}^{-}\) ions furnished by base to form one mole of water. In the light of the above statements, choose the correct answer from the options given below.

\(2.5 \mathrm{~g}\) of a non-volatile, non-electrolyte is dissolved in \(100 \mathrm{~g}\) of water at \(25^{\circ} \mathrm{C}\). The solution showed a boiling point elevation by \(2^{\circ} \mathrm{C}\). Assuming the solute concentration is negligible with respect to the solvent concentration, the vapor pressure of the resulting aqueous solution is \(\qquad\) \(\mathrm{mm}\) of \(\mathrm{Hg}\) (nearest integer) [Given : Molal boiling point elevation constant of water \(\left(\mathrm{K}_{\mathrm{b}}\right)=0.52 \mathrm{~K} . \mathrm{kg} \mathrm{mol}^{-1}\), \(1 \mathrm{~atm}\) pressure \(=760 \mathrm{~mm}\) of \(\mathrm{Hg}\), molar mass of water \(=18 \mathrm{~g} \mathrm{~mol}^{-1}\)]

Molarity \((\mathrm{M})\) of an aqueous solution containing \(x \mathrm{~g}\) of anhyd. \(\mathrm{CuSO}_4\) in \(500 \mathrm{~mL}\) solution at \(32{ }^{\circ} \mathrm{C}\) is \(2 \times 10^{-1} \mathrm{M}\). Its molality will be ______ \(\times 10^{-3} \mathrm{~m}\). (nearest integer). [Given density of the solution \(=1.25 \mathrm{~g} / \mathrm{mL}\)]