Physical Chemistry PYQ — Page 39

The standard entropy change for the reaction $4\mathrm{Fe}(s)+3{O}_{2}(g)\rightarrow 2{\mathrm{Fe}}_{2}{O}_{3}(s)$ is $-550J{K}^{-1}$ at $298K$ [Given : The standard enthalpy change for the reaction is $-165\mathrm{kJ}{\mathrm{mol}}^{-1}$]. The temperature in $K$ at which the reaction attains equilibrium is (Nearest Integer)

$1L$ aqueous solution of ${H}_{2}{\mathrm{SO}}_{4}$ contains $0.02m\mathrm{mol}{H}_{2}{\mathrm{SO}}_{4}.50%$ of this solution is diluted with deionized water to give $1L$ solution $(A)$. In solution $(A)$, $0.01m\mathrm{mol}$ of ${H}_{2}{\mathrm{SO}}_{4}$ are added. Total $m$ mols of ${H}_{2}{\mathrm{SO}}_{4}$ in the final solution is____$\times {10}^{-3}m\mathrm{moles}$.

$4.0L$ of an ideal gas is allowed to expand isothermally into vacuum until the total volume is $20L$. The amount of heat absorbed in this expansion is $L$ atm.

$\mathrm{Cu}(s)+{\mathrm{Sn}}^{2+}(0.001M)\rightarrow {\mathrm{Cu}}^{2+}(0.01M)+\mathrm{Sn}(s)$ The Gibbs free energy change for the above reaction at $298K$ is $x\times {10}^{-1}\mathrm{kJ}{\mathrm{mol}}^{-1}$. The value of $x$ is____[nearest integer] [Given : ${E}_{{\mathrm{Cu}}^{2+}/\mathrm{Cu}}^{\ominus }=0.34V;{E}_{{\mathrm{Sn}}^{2+}/\mathrm{Sn}}^{\ominus }=-0.14V;F=96500{\mathrm{Cmol}}^{-1}$]

Catalyst A reduces the activation energy for a reaction by $10\mathrm{kJ}{\mathrm{mol}}^{-1}$ at $300K$. The ratio of rate constants, $\frac{{k}_{T},\mathrm{Catalysed}}{{k}_{T},\mathrm{Uncatalysed}}$ is ${e}^{x}$. The value of $x$ is____[nearest integer] [Assume that the pre-exponential factor is same in both the cases. Given $R=8.31J{K}^{-1}{\mathrm{mol}}^{-1}$]

A student needs to prepare a buffer solution of propanoic acid and its sodium salt with $\mathrm{pH}4$. The ratio of $\frac{[{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}{\mathrm{COO}}^{-}]}{[{\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{COOH}]}$ required to make buffer is Given : ${K}_{a}({\mathrm{CH}}_{3}{\mathrm{CH}}_{2}\mathrm{COOH})=1.3\times {10}^{-5}$

The longest wavelength of light that can be used for the ionisation of lithium ion $\mathrm{(Li^{2+})}$ is $x\times {10}^{-8}m$. The value of $x$ is (Nearest Integer) (Given : Energy of the electron in the first shell of the hydrogen atom is $-2.2\times {10}^{-18}J$; $h=6.63\times {10}^{-34}\mathrm{Js}$ and $c=3\times {10}^{8}{\mathrm{ms}}^{-1}$)

$50\mathrm{mL}$ of $0.1M{\mathrm{CH}}_{3}\mathrm{COOH}$ is being titrated against $0.1M\mathrm{NaOH}$. When $25\mathrm{mL}$ of $\mathrm{NaOH}$ has been added, the $\mathrm{pH}$ of the solution will be____$\times {10}^{-2}$. (Nearest integer) (Given : ${\mathrm{pK}}_{a}({\mathrm{CH}}_{3}\mathrm{COOH})=4.76$) $\mathrm{log}2=0.30$ $\mathrm{log}3=0.48$ $\mathrm{log}5=0.69$ $\mathrm{log}7=0.84$ $\mathrm{log}11=1.04$

The neutralization occurs when $10\mathrm{mL}$ of $0.1M$ acid '$A$' is allowed to react with $30\mathrm{mL}$ of $0.05M$ base $M{(\mathrm{OH})}_{2}$. The basicity of the acid '$A$' is [$M$ is a metal]

$20\mathrm{mL}$ of $0.1M{\mathrm{NH}}_{4}\mathrm{OH}$ is mixed with $40\mathrm{mL}$ of $0.05M\mathrm{HCl}$. The $\mathrm{pH}$ of the mixture is nearest to: (Given: ${K}_{b}({\mathrm{NH}}_{4}\mathrm{OH})=1\times {10}^{-5},\mathrm{log}2=0.30$, $\mathrm{log}3=0.48,\mathrm{log}5=0.69,\mathrm{log}7=0.84$, $\mathrm{log}11=1.04$)

If the wavelength for an electron emitted from $H-$ atom is $3.3\times {10}^{-10}m$, then energy absorbed by the electron in its ground state compared to minimum energy required for its escape from the atom, is____times. [Given : $h=6.626\times {10}^{-34}\mathrm{Js}$, Mass of electron $=9.1\times {10}^{-31}$]

The electronic configuration of $\mathrm{Pt}$ (atomic number $78$) is

$20\mathrm{mL}$ of $0.02M$ hypo solution is used for the titration of $10\mathrm{mL}$ of copper sulphate solution, in the presence of excess of $\mathrm{KI}$ using starch as an indicator. The molarity of ${\mathrm{Cu}}^{2+}$ is found to be $_____\times {10}^{-2}M$ (nearest integer) Given : $2{\mathrm{Cu}}^{2+}+4{I}^{-}\rightarrow {\mathrm{Cu}}_{2}{I}_{2}+{I}_{2} {I}_{2}+2{S}_{2}{O}_{3}^{-2}\rightarrow 2{I}^{—}+{S}_{4}{O}_{6}^{-2}$

In the industrial production of which of the following, molecular hydrogen is obtained as a bye product.

Consider the cell at $25^{\circ}C$ $\mathrm{Zn}|{\mathrm{Zn}}^{2+}(\mathrm{aq}),(1M)\|{\mathrm{Fe}}^{3+}(\mathrm{aq}),{\mathrm{Fe}}^{2+}(\mathrm{aq})|\mathrm{Pt}(s)$ The fraction of total iron present as ${\mathrm{Fe}}^{3+}$ ion at the cell potential of $1.500V$ is $x\times {10}^{-2}$. The value of $x$ is ______. (Nearest integer) $\mathrm{Given}:{{E}^{\circ }}_{{\mathrm{Fe}}^{3+}|{\mathrm{Fe}}^{2+}}=0.77V,{{E}^{\circ }}_{{\mathrm{Zn}}^{2+}|\mathrm{Zn}}=-0.76V$

${\mathrm{CO}}_{2}$ gas is bubbled through water during a soft drink manufacturing process at $298K$. If ${\mathrm{CO}}_{2}$ exerts a partial pressure of $0.835\mathrm{bar}$ then $xm\mathrm{mol}$ of ${\mathrm{CO}}_{2}$ would dissolve in $0.9L$ of water. The value of $x$ is _______. (Nearest integer) (Henry's law constant for ${\mathrm{CO}}_{2}$ at $298K$ is $1.67\times {10}^{3}\mathrm{bar}$)

Gaseous cyclobutene isomerizes to butadiene in a first order process which has a '$K$' value of $3.3\times {10}^{-4}{s}^{-1}$ at $153^{\circ}C.$ The time in minutes it takes for the isomerization to proceed $40%$ to completion at this temperature is_____. (Rounded off to the nearest integer)

Of the following four aqueous solutions, the total number of those solutions whose freezing point is lower than that of $0.10{\mathrm{MC}}_{2}{H}_{5}\mathrm{OH}$ is (Integer answer) (i) $0.10M{\mathrm{Ba}}_{3}{({\mathrm{PO}}_{4})}_{2}$ (ii) $0.10M{\mathrm{Na}}_{2}{\mathrm{SO}}_{4}$ (iii) $0.10M\mathrm{KCl}$ (iv) $0.10M{\mathrm{Li}}_{3}{\mathrm{PO}}_{4}$

Which one of the following given graphs represents the variation of rate constant $(k)$ with temperature $(T)$ for an endothermic reaction?

Given below are two statements : Statement I : According to Bohr's model of an atom, qualitatively the magnitude of velocity of electron increases with decrease in positive charges on the nucleus as there is no strong hold on the electron by the nucleus. Statement II : According to Bohr's model of an atom, qualitatively the magnitude of velocity of electron increases with decrease in principle quantum number. In the light of the above statements, choose the most appropriate answer from the options given below:

In polythionic acid, ${H}_{2}{S}_{x}{O}_{6}(x=3$ to $5$) the oxidation state(s) of sulphur is/are:

The average $S-F$ bond energy in $\mathrm{kJ}{\mathrm{mol}}^{-1}$ of ${\mathrm{SF}}_{6}$ is _. (Rounded off to the nearest integer) [Given : The values of standard enthalpy of formation of ${\mathrm{SF}}_{6}(g),S(g)$ and $F(g)$ are $-1100,275$ and $80\mathrm{kJ}{\mathrm{mol}}^{-1}$ respectively.]

In which one of the following sets all species show disproportionation reaction?

A proton and a ${\mathrm{Li}}^{3+}$ nucleus are accelerated by the same potential. If ${\lambda }_{\mathrm{Li}}$ and ${\lambda }_{p}$ denote the de Broglie wavelengths of ${\mathrm{Li}}^{3+}$ and proton respectively, then the value of $\frac{{\lambda }_{\mathrm{Li}}}{{\lambda }_{p}}$ is $x\times {10}^{-1}$. The value of $x$ is _____ (Rounded off to the nearest integer) [Mass of ${\mathrm{Li}}^{3+}=8.3$ mass of proton]