Physical Chemistry PYQ — Page 21

0.5 molal aqueous solution of a weak acid $(\mathrm{HX})$ is $20 \%$ ionised. If $\mathrm{K}_f$ for water is $1.86 \mathrm{Kg} \mathrm{mol}^{-1}$, the lowering in freezing point of the solution is:

The following equilibrium constant are given: $\begin{aligned} \mathrm{N}_2+3 \mathrm{H}_2 & \rightleftharpoons 2 \mathrm{NH}_3 ; \mathrm{K}_1 \\ \mathrm{~N}_2+\mathrm{O}_2 & \rightleftharpoons 2 \mathrm{NO} ; \mathrm{K}_2 \\ \mathrm{H}_2+1 / 2 \mathrm{O}_2 & \rightleftharpoons \mathrm{H}_2 \mathrm{O} ; \mathrm{K}_3 \end{aligned}$ The equilibrium constant for the oxidation of $\mathrm{NH}_3$ by oxygen to give $\mathrm{NO}$ is:

The reaction of hydrogen and iodine monochloride is given as: $\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)} \rightarrow 2 \mathrm{HCl}_{(g)}+\mathrm{I}_{2(g)}$ This reaction is of first order with respect to $\mathrm{H}_{2(g)}$ and $\mathrm{lCl}_{(g)+}$ following mechanisms were proposed Mechanism A: $\mathrm{H}_{2(g)}+2 \mathrm{ICl}_{(g)} \rightarrow 2 \mathrm{HCl}_{(g)}+\mathrm{H}_{2(g)}$ Mechanism B: $\begin{aligned} & \mathrm{H}_{2(g)}+\mathrm{ICl}_{(g)} \rightarrow \mathrm{HCl}_{(g)}+\mathrm{HI}_{(g)} \text { :slow } \\ & \mathrm{Hl}_{(g)}+\mathrm{lCl}_{(g)} \rightarrow \mathrm{HCl}_{(g)}+\mathrm{l}_{2(g)} \text {; fast } \end{aligned}$ Which of the above mechanism(s) can be consistent with the given information about the reaction?

An element, $\mathrm{X}$ has the following isotopic composition: ${ }^{200} \mathrm{X}: 90 \% \quad{ }^{199} \mathrm{X}: 8.0 \quad{ }^{202} \mathrm{X}: 2.0 \%$ The weighted average atomic mass of the naturally-occurring element $\mathrm{X}$ is closest to

For the reaction, $2 \mathrm{~A}+\mathrm{B} \rightarrow 3 \mathrm{C}+\mathrm{D}$, which of the following does not express the reaction rate?

Which of the following pairs constitutes a buffer?

The enthalpy and entropy change for the reaction: $$ \mathrm{Br}_{2(\mathrm{l})}+\mathrm{Cl}_{2(g)} \rightarrow 2 \mathrm{BrCl}_{(g)} $$ are $30 \mathrm{~kJ} \mathrm{~mol}^{-1}$ and $105 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ respectively. The temperature which the reaction will be in equilibrium is:

Identify the correct statement for change of Gibbs energy for a system $\left(\Delta \mathrm{G}_{\text {system }}\right)$ at constant temperature and pressure:

$1.00 \mathrm{~g}$ of non-eletrolyte solute (molar mass $250 \mathrm{~g} \mathrm{~mol}^{-1}$ ) was dissolved in $51.2 \mathrm{~g}$ of benzene. If the freezing point depression constant, $\mathrm{K}_f$ of benzene is 5.12 $\mathrm{K} \mathrm{kg} \mathrm{mol}^{-1}$, the freezing point of benzene will be lowered by:

For the reaction: $$ \mathrm{CH}_{4(g)}+2 \mathrm{O}_{2(g)} \rightleftharpoons \mathrm{CO}_{2(g)}+2 \mathrm{H}_2 \mathrm{O}(l) $$ $\Delta \mathrm{H}_r=-170.8 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Which of the following statements is not true?

Consider the reaction: $\mathrm{N}_{2(g)}+3 \mathrm{H}_{2(g)} \rightarrow$ $2 \mathrm{NH}_{3(g)}$ The equality relationship between $\frac{d\left[\mathrm{NH}_3\right]}{d t}$ and $-\frac{d\left[\mathrm{H}_2\right]}{d t}$ is:

During osmosis, flow of water through a semipermeable membrane is:

The hydrogen ion concentration of a $10^{-8}$ $\mathrm{M} \mathrm{HCl}$ aqueous solution at $298 \mathrm{~K}\left(\mathrm{~K}_w=\right.$ $\left.10^{-14}\right)$ is:

The orientation of an atomic orbital is governed by:

Given: The mass of electron is $9.11 \times$ $10^{-31} \mathrm{~kg}$, Planck constant is $6.626 \times$ $10^{-34} \mathrm{Js}$. The uncertainty involved in the measurement of velocity within a distance of $0.1 Å$ is:

Assume each reaction is carried out in an open container. For which reaction will $\Delta H=\Delta E ?$

A solution of acetone in ethanol:

The enthalpy of hydrogenation of cyclohexene is $-119.5 \mathrm{~kJ} \mathrm{~mol}^{-1}$. If resoance energy of benzene is -150 $\mathrm{kJ} \mathrm{mol}^{-1}$, its enthalpy of hydrogenation would be:

A solution containing 10 g per \(\mathrm{dm}^3\) of urea (molecular mass \(=60 \mathrm{~g} \mathrm{~mol}^{-1}\)) is isotonic with a \(5 \%\) solution of a nonvolatile solute. The molecular mass of this nonvolatile solution is:

$\mathrm{E}_{\mathrm{Fe} 2+/ \mathrm{Fe}}^{\mathrm{o}}=-0.441 \mathrm{~V}$ and $\mathrm{E}_{\mathrm{Fe}^{3+} \mathrm{Fe}^{2+}}^{\mathrm{O}}=0.771$ $\mathrm{V}$, the standard EMF of the reaction $\mathrm{Fe}$ $+2 \mathrm{Fe}^{3+} \rightarrow 3 \mathrm{Fe}^{2+}$ will be:

A hypothetical electrochemical cell is show below $\stackrel{\Theta}{\mathrm{A}}\left|\mathrm{A}^{+}(x \mathrm{M}) \| \mathrm{B}^{+}(y \mathrm{M})\right| \stackrel{\oplus}{\mathrm{B}}$ The emf measured is $+0.20 \mathrm{~V}$. The cell reaction is:

The number of moles of $\mathrm{KMnO}_4$ reduced by one mole of $\mathrm{KI}$ is alkaline medium is:

The absolute enthalpy of neutralisation of the reaction: : $\mathrm{MgO}_{(s)}+2 \mathrm{HCl}_{(a q)}$ $\rightarrow \mathrm{MgCl}_{2(a q)}+\mathrm{H}_2 \mathrm{O}_{(\cap}$ will be:

$\mathrm{H}_2 \mathrm{~S}$ gas when passed through a solution of cations containing $\mathrm{HCl}$ precipitates the cations of second group of qualitative analysis but not those belonging to the fourth group. It is because