Physical Chemistry PYQ — Page 66

$6$ litres of an alkene require $27$ litres of oxygen at constant temperature and pressure for complete combustion. The alkene is :

What is the $\mathrm{pH}$ of a $10^{-4} \mathrm{M} \mathrm{OH}^{-}$solution at $330 \mathrm{~K}$, if $\mathrm{K}_{\mathrm{w}}$ at $330 \mathrm{~K}$ is $10^{-13.6}$ ?

Values of dissociation constant, $K_a$ are given as follows : $\begin{array}{lc}\text { Acid } & \boldsymbol{K}_{\boldsymbol{a}} \\ \mathrm{HCN} & 6.2 \times 10^{-10} \\ \mathrm{HF} & 7.2 \times 10^{-4} \\ \mathrm{HNO}_2 & 4.0 \times 10^{-4}\end{array}$ Correct order of increasing base strength of the base $\mathrm{CN}^{-}, \mathrm{F}^{-}$and $\mathrm{NO}_2^{-}$will be :

A gaseous hydrocarbon on combustion gives $0.72g$ of water and $3.08g$ ${\mathrm{CO}}_{2}$. What is the empirical formula of the hydrocarbon?

The rate of a reaction doubles when its temperature changes from $300K\mathrm{to}310K$. Activation energy of such a reaction will be: $(\text{R}={\text{8.314 JK}}^{-1}{mol}^{-1}\mathrm{and}log 2=\text{0.301})$

A solution of copper sulphate $\left(\mathrm{CuSO}_4\right)$ is electrolysed for $10$ minutes with a current of $1.5$ amperes. The mass of copper deposited at the cathode (at. mass of $\mathrm{Cu}=63 \mathrm{u}$ ) is :

The reaction $\mathrm{X} \rightarrow \mathrm{Y}$ is an exothermic reaction. Activation energy of the reaction for $\mathrm{X}$ into $\mathrm{Y}$ is $150 \mathrm{~kJ} \mathrm{~mol}^{-1}$. Enthalpy of reaction is $135 \mathrm{~kJ}$ $\mathrm{mol}^{-1}$. The activation energy for the reverse reaction, $\mathrm{Y} \rightarrow \mathrm{X}$ will be :

Given (A) $\mathrm{n}=5, \mathrm{~m}_{\ell}=+1$ (B) $\mathrm{n}=2, \ell=1, \mathrm{~m}_{\ell}=-1, \mathrm{~m}_{\mathrm{s}}=-\mathrm{l} / 2$ The maximum number of electron(s) in an atom that can have the quantum numbers as given in (A) and (B) are respectively:

Energy of an electron is given by $\text{E}=-2\text{.}178\times 1{0}^{-18}(\frac{{\text{Z}}^{2}}{{\text{n}}^{2}})\text{ J}$. Wavelength of light required to excite an electron in a hydrogen atom from level n=1 to n=2 will be : $(\text{h}=6.62\times {10}^{-34} \text{J} \text{s} \text{a}\text{n}\text{d} \text{c}=3.0\times {10}^{8} \text{m}{\text{s}}^{-1})$

In reaction $\mathrm{A}+2 \mathrm{~B} \rightleftharpoons 2 \mathrm{C}+\mathrm{D}$, initial concentration of $\mathrm{B}$ was $1.5$ times of $\mathrm{[A]}$, but at equilibrium the concentrations of $\mathrm{A}$ and $\mathrm{B}$ became equal. The equilibrium constant for the reaction is :

A piston filled with 0.04 mol of an ideal gas expands reversibly from 50.0 mL to 375 mL at a constant temperature of $3 7 . {0}^{\circ } \text{C}$. As it does so, it absorbs 208 J of heat. The values of q and w for the process will be (R = 8.314 J/mol K) (ln7.5 = 2.01)

Consider the following reaction: $x {\mathrm{MnO}}_{4}^{-}+y {C}_{2}{O}_{4}^{2-}+{\mathrm{zH}}^{+}\longrightarrow x {\mathrm{Mn}}^{2+}+2y {\mathrm{CO}}_{2}+\frac{z}{2}{H}_{2}O$ The values of x, y and z in the reaction are, respectively:

Which of the following statements/relationships is not correct in thermodynamic changes ?

In which of the following exothermic reactions, the heat liberated per mole is the highest ?

Number of atoms in the following samples of substances is largest in:

Solid $\mathrm{Ba}\left(\mathrm{NO}_3\right)_2$ is gradually dissolved in a $1.0 \times 10^{-4} \mathrm{~M} \mathrm{~Na}_2 \mathrm{CO}_3$ solution. At which concentration of $\mathrm{Ba}^{2+}$, precipitate of $\mathrm{BaCO}_3$ begins to form ? $\left(K_{s p}\right.$ for $\left.\mathrm{BaCO}_3=5.1 \times 10^{-9}\right)$

The de Broglie wavelength of a car of mass 1000 $\mathrm{kg}$ and velocity $36 \mathrm{~km} / \mathrm{hr}$ is :

Electrode potentials $\left(\mathrm{E}^{\circ}\right)$ are given below : $\begin{aligned} & \mathrm{Cu}^{+} / \mathrm{Cu}=+0.52 \mathrm{~V} ,\\ & \mathrm{Fe}^{3+} / \mathrm{Fe}^{2+}=+0.77 \mathrm{~V}, \\ & \frac{1}{2} \mathrm{I}_2(\mathrm{~s}) / \mathrm{I}^{-}=+0.54 \mathrm{~V}, \\ & \mathrm{Ag}^{+} / \mathrm{Ag}=+0.88 \mathrm{~V}. \end{aligned}$ Based on the above potentials, strongest oxidizing agent will be :

(1) $\mathrm{N}_2(\mathrm{~g})+3 \mathrm{H}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NH}_3(\mathrm{~g}), \mathrm{K}_1$ (2) $\mathrm{N}_2(\mathrm{~g})+\mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g}), \mathrm{K}_2$ (3) $\mathrm{H}_2(\mathrm{~g})+\frac{1}{2} \mathrm{O}_2(\mathrm{~g}) \rightleftharpoons \mathrm{H}_2 \mathrm{O}(\mathrm{g}), \mathrm{K}_3$ The equation for the equilibrium constant of the reaction $$ 2 \mathrm{NH}_3(\mathrm{~g})+\frac{5}{2} \mathrm{O}_2(\mathrm{~g}) \rightleftharpoons 2 \mathrm{NO}(\mathrm{g})+3 \mathrm{H}_2 \mathrm{O}(\mathrm{g}) \text {, } $$ $\left(K_4\right)$ in terms of $\mathrm{K}_1, \mathrm{~K}_2$ and $\mathrm{K}_3$ is :

A radioactive isotope having a half - life period of $3$ days was received after $12$ days. If $3 \mathrm{~g}$ of the isotope is left in the container, what would be the initial mass of the isotope ?

Given : $\mathrm{XNa}_2 \mathrm{HAsO}_3+\mathrm{YNaBrO}_3+\mathrm{ZHCl} \rightarrow \mathrm{NaBr}+\mathrm{H}_3 \mathrm{AsO}_4+\mathrm{NaCl}$ The values of $\mathrm{X}, \mathrm{Y}$ and $\mathrm{Z}$ in the above redox reaction are respectively :

The molarity of a solution obtained by mixing $750\mathrm{mL}$ of $0.5(M)\mathrm{HCl}$ with $250\mathrm{mL}$ of $2(M)\mathrm{HCl}$ will be

What would be the $\mathrm{pH}$ of a solution obtained by mixing $5 \mathrm{~g}$ of acetic acid and $7.5 \mathrm{~g}$ of sodium acetate and making the volume equal to $500 \mathrm{~mL}$ ? $\left(\mathrm{K}_{\mathrm{a}}=1.75 \times 10^{-5}, \mathrm{pK}_{\mathrm{a}}=4.76\right)$

The density of $3 \mathrm{M}$ solution of sodium chloride is $1.252 \mathrm{~g} \mathrm{~mL}^{-1}$. The molality of the solution will be : $\left(\right.$ molar mass, $\left.\mathrm{NaCl}=585 \mathrm{~g} \mathrm{~mol}^{-1}\right)$