Physical Chemistry PYQ — Page 9

In a first order decomposition reaction, the time taken for the decomposition of reactant to one fourth and one eighth of its initial concentration are $t_1$ and $t_2(s)$, respectively. The ratio $t_1 / t_2$ will :

When a non-volatile solute is added to the solvent, the vapour pressure of the solvent decreases by 10 mm of Hg . The mole fraction of the solute in the solution is 0.2 . What would be the mole fraction of the solvent if decrease in vapour pressure is 20 mm of Hg ?

Arrange the following in increasing order of solubility product : $\mathrm{Ca}(\mathrm{OH})_2, \mathrm{AgBr}, \mathrm{PbS}, \mathrm{HgS}$

Half life of zero order reaction $\mathrm{A} \rightarrow$ product is 1 hour, when initial concentration of reaction is $2.0 \mathrm{~mol} \mathrm{~L} \mathrm{~L}^{-1}$. The time required to decrease concentration of A from 0.50 to $0.25 \mathrm{~mol} \mathrm{~L}^{-1}$ is:

If \(A_2 B\) is \(30 \%\) ionised in an aqueous solution, then the value of van't Hoff factor (i) is ______ \(\times 10^{-1}\).

For the reaction $\mathrm{A} \rightarrow \mathrm{B}$ the following graph was obtained. The time required (in seconds) for the concentration of A to reduce to $2.5 \mathrm{~g} \mathrm{~L}^{-1}$ (if the initial concentration of A was $50 \mathrm{~g} \mathrm{~L}^{-1}$) is _______ (Nearest integer) Given : $\log 2=0.3010$ [We can assume in a hypothetical situation that the graph is correct, assuming its first order reaction, in reality the question is wrong.] 

Xg of benzoic acid on reaction with aq $\mathrm{NaHCO}_3$ released $\mathrm{CO}_2$ that occupied 11.2 L volume at STP. X is _____ g.

If 1 mM solution of ethylamine produces $\mathrm{pH}=9$, then the ionization constant $\left(\mathrm{K}_{\mathrm{b}}\right)$ of ethylamine is $10^{-x}$. The value of $x$ is ______ (nearest integer). [The degree of ionization of ethylamine can be neglected with respect to unity.]

Consider the following electrochemical cell at standard condition. \(\begin{aligned} & \mathrm{Au}(\mathrm{s})\left|\mathrm{QH}_2, \mathrm{Q}\right| \mathrm{NH}_4 \mathrm{X}(0.01 \mathrm{M})| | \mathrm{Ag}^{+}(1 \mathrm{M}) \mid \mathrm{Ag}(\mathrm{s}) \\ & \mathrm{E}_{\text {cell }}=+0.4 \mathrm{~V} \end{aligned}\) The couple \(\mathrm{QH}_2 / \mathrm{Q}\) represents quinhydrone electrode, the half cell reaction is given below  The \(\mathrm{pK}_{\mathrm{b}}\) value of the ammonium halide salt \(\left(\mathrm{NH}_4 \mathrm{X}\right)\) used here is _________. (nearest integer)

$1$ Faraday electricity was passed through $\mathrm{Cu}^{2+}(1.5$ $\mathrm{M}, 1 \mathrm{~L}) / \mathrm{Cu}$ and $0.1$ Faraday was passed through $\mathrm{Ag}^{+}(0.2 \mathrm{M}, 1 \mathrm{~L}) / \mathrm{Ag}$ electrolytic cells. After this the two cells were connected as shown below to make an electrochemical cell. The emf of the cell thus formed at 298 K is-  Given: $\mathrm{E}_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\mathrm{o}}=0.34 \mathrm{~V}$ $\mathrm{E}_{\mathrm{Ag}^{+} / \mathrm{Ag}}^0=0.8 \mathrm{~V}$ $\frac{2.303 \mathrm{RT}}{\mathrm{F}}=0.06 \mathrm{~V}$

One mole of an ideal gas expands isothermally and reversibly from $10 \mathrm{dm}^3$ to $20 \mathrm{dm}^3$ at $300 \mathrm{~K}. \Delta \mathrm{U}$, q and work done in the process respectively are : Given : $\mathrm{R}=8.3 \mathrm{JK}^{-1}$ and $\mathrm{mol}^{-1}$ $\begin{aligned}<br />& \text { In } 10=2.3 \\ & \log 2=0.30 \\ & \log 3=0.48<br />\end{aligned}$

For $\mathrm{A}_2+\mathrm{B}_2 \rightleftharpoons 2 \mathrm{AB}$ $\mathrm{E}_{\mathrm{a}}$ for forward and backward reaction are 180 and $200 \mathrm{~kJ} \mathrm{~mol}^{-1}$ respectively If catalyst lowers $\mathrm{E}_{\mathrm{a}}$ for both reaction by $100 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Which of the following statement is correct?

Given below are two statements : Statement (I) : For a given shell, the total number of allowed orbitals is given by $\mathrm{n}^2$. Statement (II) : For any subshell, the spatial orientation of the orbitals is given by $-l$ to $+l$ values including zero. In the light of the above statements, choose the correct answer from the options given below :

The pH of a 0.001 M HCl solution is:

An aqueous solution of HCl with pH 1.0 is diluted by adding equal volume of water (ignoring dissociation of water). The pH of HCl solution would (Given $\log 2=0.30)$

Density of 3 M NaCl solution is $1.25 \mathrm{~g} / \mathrm{mL}$. The molality of the solution is :

For the given cell $\mathrm{Fe}^{2+}{ }_{(\mathrm{aq})}+\mathrm{Ag}^{+}{ }_{(\mathrm{aq})} \rightarrow \mathrm{Fe}_{(\mathrm{aq})}^{3+}+\mathrm{Ag}_{(\mathrm{s})}$ The standard cell potential of the above reaction is Given: $\begin{array}{lr} \mathrm{Ag}^{+}+\mathrm{e}^{-} \rightarrow \mathrm{Ag} & \mathrm{E}^\theta=\mathrm{xV} \\ \mathrm{Fe}^{2+}+2 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^\theta=\mathrm{yV} \\ \mathrm{Fe}^{3+}+3 \mathrm{e}^{-} \rightarrow \mathrm{Fe} & \mathrm{E}^\theta=\mathrm{zV} \end{array}$

Rate law for a reaction between A and B is given by $\mathrm{R}=\mathrm{k}[\mathrm{~A}]^{\mathrm{n}}[\mathrm{~B}]^{\mathrm{m}}$ If concentration of A is doubled and concentration of $B$ is halved from their initial value, the ratio of new rate of reaction to the initial rate of reaction $\left(\frac{r_2}{r_1}\right)$ is

Total number of non bonded electrons present in $\mathrm{NO}_2{ }^{-}$ion based on Lewis theory is

$2.8 \times 10^{-3} \mathrm{~mol}$ of $\mathrm{CO}_2$ is left after removing $10^{21}$ molecules from its ' $x$ ' mg sample. The mass of $\mathrm{CO}_2$ taken initially is Given: $\mathrm{N}_{\mathrm{A}}=6.02 \times 10^{23} \mathrm{~mol}^{-1}$

Based on the data given below : $\begin{array}{ll}\mathrm{E}_{\mathrm{Cr}_2 \mathrm{O}_7^{2-} / \mathrm{Cr}^{3+}}^{\circ}=1.33 \mathrm{~V} & \mathrm{E}_{\mathrm{Cl}_2 / \mathrm{Cl}^{(-)}}^{\circ}=1.36 \mathrm{~V} \\ \mathrm{E}_{\mathrm{MnO}_4^{-} / \mathrm{Mn}^{2+}}^{\circ}=1.51 \mathrm{~V} & \mathrm{E}_{\mathrm{Cr}^{3+} / \mathrm{Cr}}^{\circ}=-0.74 \mathrm{~V}\end{array}$ the strongest reducing agent is :

Given below are two statements : Statement (I) : It is impossible to specify simultaneously with arbitrary precision, both the linear momentum and the position of a particle. Statement (II) : If the uncertainty in the measurement of position and uncertainty in measurement of momentum are equal for an electron, then the uncertainty in the measurement of velocity is $\geqslant \sqrt{\frac{\mathrm{h}}{\pi}} \times \frac{1}{2 \mathrm{~m}}$. In the light of the above statements, choose the correct answer from the options given below :

Given below are two statements : Statement (\(\mathbf{I}\)): The radii of isoelectronic species increases in the order. \(\mathrm{Mg}^{2+} \lt \mathrm{Na}^{+} \lt \mathrm{F}^{-} \lt \mathrm{O}^{2-}\) Statement (II): The magnitude of electron gain enthalpy of halogen decreases in the order. \(\mathrm{Cl}\gt\mathrm{F}\gt\mathrm{Br}\gt\mathrm{I}\) In the light of the above statements, choose the most appropriate answer from the options given below :

Which of the following postulate of Bohr's model of hydrogen atom in not in agreement with quantum mechanical model of an atom ?