Chapter 7

An example of a reversible reaction is : (a) \(\mathrm{Pb}\left(\mathrm{NO}_{3}\right)_{2} \mathrm{aq}+2 \mathrm{NaI}(\mathrm{aq}) \rightarrow \mathrm{PbI}_{2}(\mathrm{~s})+2 \mathrm{NaNO}_{3}(\mathrm{aq})\) (b) \(\mathrm{AgNO}_{3}(\mathrm{aq})+\mathrm{HCl}(\mathrm{aq}) \rightarrow \mathrm{AgCl}(\mathrm{s})+\mathrm{NaNO}_{3}(\mathrm{aq})\) (c) \(2 \mathrm{Na}(\mathrm{s})+\mathrm{H}_{2} \mathrm{O}(1) \rightarrow 2 \mathrm{NaOH}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})\) (d) \(\mathrm{KNO}_{3}(\mathrm{aq})+\mathrm{NaCl}(\mathrm{aq}) \rightarrow \mathrm{KCl}(\mathrm{aq})+\mathrm{NaNO}_{3}(\mathrm{aq})\)

The following equilibrium is established when hydrogen chloride is dissolved in acetic acid. $$ \mathrm{HCl}+\mathrm{CH}_{3} \mathrm{COOH} \rightleftharpoons \mathrm{Cl}^{-}+\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+} $$ The set that characterises the conjugate acid-base pairs is (a) \(\left(\mathrm{HCl}, \mathrm{CH}_{3} \mathrm{COOH}\right)\) and \(\left(\mathrm{CH}_{2} \mathrm{COOH}_{2}^{+}, \mathrm{Cl}^{-}\right)\) (b) \(\left(\mathrm{HCl}, \mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}\right)\)and \(\left(\mathrm{CH}_{3} \mathrm{COOH}, \mathrm{Cl}^{-}\right)\) (c) \(\left(\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{HCl}\right)\) and \(\left(\mathrm{Cl}^{-}, \mathrm{CH}_{3} \mathrm{COOH}\right)\) (d) \(\left(\mathrm{HCl}, \mathrm{Cl}^{-}\right)\)and \(\left(\mathrm{CH}_{3} \mathrm{COOH}_{2}^{+}, \mathrm{CH}_{3} \mathrm{COOH}\right)\)

A liquid is in equilibrium with its vapour at its boiling point. On the average, the molecules in the two phases have equal : (a) inter-molecular forces (b) potential energy (c) total energy (d) kinetic energy

The precipitate of $$\mathrm{CaF}_{2}\left(K_{s p}=1.7 \times 10^{-10}\right)$$ is obtained when equal volumes of the following are mixed (a) \(10^{-4} \mathrm{M} \mathrm{Ca}^{2+}+10^{-4} \mathrm{M} \mathrm{F}^{-}\) (b) \(10^{-2} \mathrm{M} \mathrm{Ca}^{2+}+10^{-3} \mathrm{M} \mathrm{F}^{-}\) (c) \(10^{-5} \mathrm{M} \mathrm{Ca}^{2+}+10^{-3} \mathrm{M} \mathrm{F}^{-}\) (d) \(10^{-3} \mathrm{M} \mathrm{Ca}^{2+}+10^{-5} \mathrm{M} \mathrm{F}^{-}\)

The \(\mathrm{p} K_{a}\) of acetylsalicyclic and (aspirin) is \(3.5\). The \(\mathrm{pH}\) of gastric juice in human stomach is about \(2-3\) and the \(\mathrm{pH}\) in the small intestine is about 8. Aspirin will be (a) unionised in the small intestine and in the stomach (b) completely ionised in the small intestine and in the stomach (c) ionised in the stomach and almost unionised in the small intestine (d) ionised in the small intestine and almost unionised in the stomach.

For the reaction : $$\mathrm{H}_{2}(\mathrm{~g})+\mathrm{I}_{2}(\mathrm{~g}) \rightleftharpoons 2 \mathrm{HI}(\mathrm{g})$$ the equilibrium constant \(K_{p}\) changes with (a) total pressure (b) catalyst (c) the amounts of \(\mathrm{H}_{2}\) and \(\mathrm{I}_{2}\) present (d) temperature

The compound whose \(0.1 \mathrm{M}\) solution is basic is : (a) ammonium acetate (b) ammonium chloride (c) ammonium sulphate (d) sodium acetate

The oxidation of \(\mathrm{SO}_{2}\) by \(\mathrm{O}_{2}\) to \(\mathrm{SO}_{3}\) is an exothermic reaction. The yield of \(\mathrm{SO}_{3}\) will be maximum if [1981-1 Mark] (a) temperature is increased and pressure is kept constant (b) temperature is reduced and pressure is increased (c) both temperature and pressure are increased (d) both temperature and pressure are reduced

The compound insoluble in acetic acid is : (a) calcium oxide (b) calcium carbonate (c) calcium oxalate (d) calcium hydroxide

Molten sodium chloride conducts electricitry due to the presence of [1981-1 Mark] (a) free electrons (b) free ions (c) free molecules (d) atoms of sodium and chlorine

The compound that is not a Lewis acid is : (a) \(\mathrm{BF}_{3}\) (b) \(\mathrm{AlCl}_{3}\) (c) \(\mathrm{BeCl}_{2}\) (d) \(\mathrm{SnCl}_{4}\)

In 1 L saturated solution of \(\mathrm{AgCl}\left[\mathrm{Ksp}(\mathrm{AgCl})=1.6 \times 10^{-10}\right], 0.1 \mathrm{~mol}\) of \(\mathrm{CuCl}\left[K_{s p}(\mathrm{CuCl})=1.0 \times 10^{-6}\right]\) is added. The resultant concentration of \(\mathrm{Ag}^{+}\)in the solution is \(1.6 \times 10^{-x}\). The value of " \(x\) " is

The conjugate acid of \(\mathrm{NH}_{2}^{-}\)is : (a) \(\mathrm{NH}_{3}\) (b) \(\mathrm{NH}_{2} \mathrm{OH}\) (c) \(\mathrm{NH}_{4}^{+}\) (d) \(\mathrm{N}_{2} \mathrm{H}_{4}\)

The best indicator for detection of end point in titration of a weak acid and a strong base is : (a) methyl orange ( 3 to 4 ) (b) methyl red (5 to 6) (c) bromothymol blue ( 6 to \(7.5\) ) (d) phenolphthalein ( 8 to \(9.6\) )

For a reaction \(\mathrm{X}+\mathrm{Y} \rightleftharpoons 2 \mathrm{Z}, 1.0 \mathrm{~mol}\) of \(\mathrm{X}, 1.5 \mathrm{~mol}\) of \(\mathrm{Y}\) and \(0.5 \mathrm{~mol}\) of \(Z\) were taken in a 1 L vessel and allowed to react. At equilibrium, the concentration of \(Z\) was \(1.0 \mathrm{~mol} \mathrm{~L}^{-1} .\) The equilibrium constant of the reaction is \(\frac{x}{15} .\) The value of \(x\) is _________.

A certain buffer solution contains equal concentration of \(X^{-}\)and \(H X\). The \(K_{b}\) for \(X^{-}\)is \(10^{-10} .\) The \(\mathrm{pH}\) of the buffer is: (a) 4 (b) 7 (c) 10 (d) 14

For the following reaction, the equilibrium constant \(K_{c}\) at \(298 \mathrm{~K}\) is \(1.6\) \(\times 10^{17}\) $$ \mathrm{Fe}^{2+}(\mathrm{aq})+\mathrm{S}^{2-}(\mathrm{aq}) \rightleftharpoons \mathrm{FeS}(\mathrm{s}) $$ When equal volumes of \(0.06 \mathrm{M} \mathrm{Fe}^{2+}\) (aq) and \(0.2 \mathrm{M} \mathrm{S}^{2-}\) (aq) solutions are mixed, the equilibrium concentration of \(\mathrm{Fe}^{2+}\) (aq) is found to be \(Y \times\) \(10^{-17} \mathrm{M}\). The value of \(Y\) is

An aqueous solution of a metal bromide \(M \mathrm{Br}_{2}(0.05 \mathrm{M})\) is saturated with \(\mathrm{H}_{2} \mathrm{~S}\). What is the minimum \(\mathrm{pH}\) at which \(M \mathrm{~S}\) will precipitate? [1993 - 3 Marks] \(K_{s p}\) for \(M \mathrm{~S}=6.0 \times 10^{-21} ;\) concentration of saturated \(\mathrm{H}_{2} \mathrm{~S}=0.1 \mathrm{M}\) \(K_{1}=10^{-7}\) and \(K_{2}=1.3 \times 10^{-13}\), for \(\mathrm{H}_{2} \mathrm{~S}\).

At \(90^{\circ} \mathrm{C}\), pure water has \(\left[\mathrm{H}_{3} \mathrm{O}^{+}\right] 10^{-6}\) mole litre \(^{-1}\). What is the value of \(K_{\mathrm{w}}\) at \(90^{\circ} \mathrm{C} ?\) (a) \(10^{-6}\) (b) \(10^{-12}\) (c) \(10^{-14}\) (d) \(10^{-8}\)

Of the given anions, the strongest Bronsted base is (a) \(\mathrm{ClO}^{-}\) (b) \(\mathrm{Cl} \mathrm{O}_{2}^{-}\) (c) \(\mathrm{Cl} \mathrm{O}_{3}^{-}\) (d) \(\mathrm{Cl} \mathrm{O}_{4}^{-}\)

A ten-fold increase in pressure on the reaction, \(\mathrm{N}_{2}(\mathrm{~g})+3 \mathrm{H}_{2}(\mathrm{~g}) \rightleftharpoons\) \(2 \mathrm{NH}_{3}(\mathrm{~g})\) at equilibrium results in \(\ldots .\) in \(K_{P}\)

An acidic buffer solution can be prepared by mixing the solutions of (a) ammonium acetate and acetic acid (b) ammonium chloride and ammonioum hydroxide (c) sulphuric acid and sodium sulphate (d) sodium chloride and sodium hydroxide.

Solubility of sodium hydroxide increases with increase in temperature.

Amongst the following, the total number of compounds whose aqueous solution turns red litmus paper blue is \(\mathrm{KCN}, \mathrm{K}_{2} \mathrm{SO}_{4},\left(\mathrm{NH}_{4}\right)_{2} \mathrm{C}_{2} \mathrm{O}_{4}, \mathrm{NaCl}, \mathrm{Zn}\left(\mathrm{NO}_{3}\right)_{2}, \mathrm{FeCl}_{3}, \mathrm{~K}_{2} \mathrm{CO}_{3}, \mathrm{NH}_{4} \mathrm{NO}_{3}\) and \(\mathrm{LiCN}\)

The total number of diprotic acids among the following is: \(\mathrm{H}_{3} \mathrm{PO}_{4}, \mathrm{H}_{2} \mathrm{SO}_{4}, \mathrm{H}_{3} \mathrm{PO}_{3}, \mathrm{H}_{2} \mathrm{CO}_{3}, \mathrm{H}_{2} \mathrm{~S}_{2} \mathrm{O}_{7}, \mathrm{H}_{3} \mathrm{BO}_{3}, \mathrm{H}_{3} \mathrm{PO}_{2}, \mathrm{H}_{2} \mathrm{CrO}_{4}\) and \(\mathrm{H}_{2} \mathrm{SO}_{3}\)

The dissociation constant of a substituted benzoic acid at \(25^{\circ} \mathrm{C}\) is \(1.0\) \(\times 10^{-4}\). The \(\mathrm{pH}\) of a \(0.01 \mathrm{M}\) solution of its sodium salt is

The thermal dissociation equilibrium of \(\mathrm{CaCO}_{3}\) (s) is studied under different conditions \(\mathrm{CaCO}_{3}(\mathrm{~s}) \rightleftharpoons \mathrm{CaO}(\mathrm{s})+\mathrm{CO}_{2}(\mathrm{~g}) .\) For this equilibrium, the correct statement(s) is (are) (a) \(\Delta H\) is dependent on \(T\) (b) \(K\) is independent of the initial amount of \(\mathrm{CaCO}_{3}\) (c) \(K\) is dependent on the pressure of \(\mathrm{CO}_{2}\) at a given \(T\) (d) \(\Delta H\) is independent of catalyst, if any

\(0.1 \mathrm{M} \mathrm{NaOH}\) is titrated with \(0.1 \mathrm{M} \mathrm{H} A\) till the end point; \(K_{a}\) for \(\mathrm{H} A\) is \(5.6 \times 10^{-6}\) and degree of hydrolysis is less compared to 1. Calculate \(\mathrm{pH}\) of the resulting solution at the end point.

The \(K_{s p}\) of \(\mathrm{Ag}_{2} \mathrm{CrO}_{4}\) is \(1.1 \times 10^{-12}\) at \(298 \mathrm{~K}\). The solubility (in \(\mathrm{mol} / \mathrm{L}\) ) of \(\mathrm{Ag}_{2} \mathrm{CrO}_{4}\) in a \(0.1 \mathrm{M} \mathrm{AgNO}_{3}\) solution is (a) \(1.1 \times 10^{-11}\) (b) \(1.1 \times 10^{-10}\) (c) \(1.1 \times 10^{-12}\) (d) \(1.1 \times 10^{-9}\)

An acid type indicator, HIn differs in colour from its conjugate base (In \(^{-}\)). The human eye is sensitive to colour differences only when the ratio \(\left[\mathrm{In}^{-}\right] /[\mathrm{HIn}]\) is greater than 10 or smaller than. \(0.1\). What should be the minimum change in the \(\mathrm{pH}\) of the solution to observe a complete colour change \(\left(K_{a}=1.0 \times 10^{-5}\right) ?\)

For the reaction \(\mathrm{CO}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) \rightleftharpoons \mathrm{CO}_{2}(\mathrm{~g})+\mathrm{H}_{2}(\mathrm{~g})\) at a given temperature, the equilibrium amount of \(\mathrm{CO}_{2}(\mathrm{~g})\) can be increased by [1998 - 2 Marks] (a) adding a suitable catalyst (b) adding an inert gas (c) decreasing the volume of the container (d) increasing the amount of \(\mathrm{CO}(\mathrm{g})\).

For the reaction : $$ \mathrm{PCl}_{5}(\mathrm{~g}) \rightarrow \mathrm{PCl}_{3}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) $$ The forward reaction at constant temperature is favoured by (a) introducing an inert gas at constant volume (b) introducing chlorine gas at constant volume (c) introducing an inert gas at constant pressure (d) increasing the volume of the container (e) introducing \(\mathrm{PCl}_{5}\) at constant volume

\(3 \mathrm{~g}\) of acetic acid is added to \(250 \mathrm{~mL}\) of \(0.1 \mathrm{M} \mathrm{HCl}\) and the solution made up to \(500 \mathrm{~mL}\). To \(20 \mathrm{~mL}\) of this solution \(\frac{1}{2} \mathrm{~mL}\) of \(5 \mathrm{M} \mathrm{NaOH}\) is added. The \(\mathrm{pH}\) of the solution is [Given: pKa of acetic acid \(=4.75\), molar mass of acetic acid \(=60 \mathrm{~g} / \mathrm{mol}\), $$ \log 3=0.4771] $$ Neglect any changes in volume.

The equilibrium : $$ \begin{gathered} \text { [1989-1 Mark] } \\ \mathrm{SO}_{2} \mathrm{Cl}_{2}(\mathrm{~g}) \rightleftharpoons \mathrm{SO}_{2}(\mathrm{~g})+\mathrm{Cl}_{2}(\mathrm{~g}) \end{gathered} $$ is attained at \(25^{\circ} \mathrm{C}\) in a closed container and an inert gas, helium is introduced. Which of the following statements are correct? (a) Concentration of \(\mathrm{SO}_{2}, \mathrm{Cl}_{2}\) and \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) do not change (b) More chlorine is formed (c) Concentration of \(\mathrm{SO}_{2}\) is reduced (d) More \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) is formed.

If the solubility product of \(\mathrm{AB}_{2}\) is \(3.20 \times 10^{-11} \mathrm{M}^{3}\), then the solubility of \(\mathrm{AB}_{2}\) in pure water is \(\times 10^{-4} \mathrm{~mol} \mathrm{~L}^{-1}\). [Assuming that neither kind of ion reacts with water]

When \(\mathrm{NaNO}_{3}\) is heated in a closed vessel, oxygen is liberated and \(\mathrm{NaNO}_{2}\) is left behind. At equilibrium. [1986-1 Mark] (a) addition of \(\mathrm{NaNO}_{2}\) favours reverse reaction (b) addition of \(\mathrm{NaNO}_{3}\) favours forward reaction (c) increasing temperature favours forward reaction (d) increasing pressure favours reverse reaction

An acidified solution of \(0.05 \mathrm{M} \mathrm{Zn}^{2+}\) is saturated with \(0.1 \mathrm{M} \mathrm{H}_{2} \mathrm{~S}\). What is the minimum molar concentration (M) of \(\mathrm{H}^{+}\)required to prevent the precipitation of \(\mathrm{ZnS}\) ? Use \(K_{\mathrm{sp}}(\mathrm{ZnS})=1.25 \times 10^{-22}\) and overall dissociation constant of \(\mathrm{H}_{2} \mathrm{~S}, K_{\mathrm{NET}}\) \(=K_{1} K_{2}=1 \times 10^{-21} . \quad\)

For the gas phase reaction : $$\mathrm{C}_{2} \mathrm{H}_{4}+\mathrm{H}_{2} \rightleftharpoons \mathrm{C}_{2} \mathrm{H}_{6}(\Delta H=-32.7 \mathrm{kcal})$$ carried out in a vessel, the equilibrium concentration of \(\mathrm{C}_{2} \mathrm{H}_{4}\) can be increased by : (a) increasing the temperature (b) decreasing the pressure (c) removing some \(\mathrm{H}_{2}\) (d) adding some \(\mathrm{C}_{2} \mathrm{H}_{6}\)

The solubility of a salt of weak acid \((A B)\) at \(\mathrm{pH} 3\) is \(\boldsymbol{Y} \times 10^{-3} \mathrm{~mol} \mathrm{~L}^{-1}\). The value of \(\boldsymbol{Y}\) is (Given that the value of solubility product of \(\boldsymbol{A B}\) \(\left(K_{s p}\right)=2 \times 10^{-10}\) and the value of ionization constant of \(\left.\boldsymbol{H B}\left(K_{a}\right)=1 \times 10^{-8}\right)\)

Each question contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason). Each question has 5 choices (a), (b), (c) and (d) out of which ONLY ONE is correct. Mark your answer as Statement \(-1\) For every chemical reaction at equilibrium, standard Gibbs energy of reaction is zero. Statement \(-2\) At constant temperature and pressure, chemical reactions are spontaneous in the direction of decreasing Gibbs energy.

The average concentration of \(\mathrm{SO}_{2}\) in the atmosphere over a city on a certain day is \(10 \mathrm{ppm}\), when the average temperature is \(298 \mathrm{~K}\). Given that the solubility of \(\mathrm{SO}_{2}\) in water at \(298 \mathrm{~K}\) is \(1.3653\) moles litre \(^{-1}\) and the \(\mathrm{p} K_{a}\) of \(\mathrm{H}_{2} \mathrm{SO}_{3}\) is \(1.92\), estimate the \(\mathrm{pH}\) of rain on that day.

What will be the resultant \(\mathrm{pH}\) when \(200 \mathrm{~mL}\) of an aqueous solution of \(\mathrm{HCl}(\mathrm{pH}=2.0)\) is mixed with \(300 \mathrm{~mL}\) of an aqueous solution of \(\mathrm{NaOH}(\mathrm{pH}=12.0) ?\)

When \(3.06 \mathrm{~g}\) of solid \(\mathrm{NH}_{4} \mathrm{HS}\) is introduced into a two litre evacuated flask at \(27^{\circ} \mathrm{C}, 30 \%\) of the solid decomposes into gaseous ammonia and hydrogen sulphide. (i) Calculate \(K_{c}\) and \(K_{p}\) for the reaction at \(27^{\circ} \mathrm{C}\). (ii) What would happen to the equilibrium when more solid \(\mathrm{NH}_{4} \mathrm{HS}\) is introduced into the flask?

What is the \(\mathrm{pH}\) of a \(0.50 \mathrm{M}\) aqueous \(\mathrm{NaCN}\) solution? \(\mathrm{p} K_{b}\) of \(\mathrm{CN}^{-}\)is \(4.70\)

Given : \(\mathrm{Ag}\left(\mathrm{NH}_{3}\right)_{2}^{+} \rightleftharpoons \mathrm{Ag}^{+}+2 \mathrm{NH}_{3}, K_{c}=6.2 \times 10^{-8}\) and \(K_{s p}\) of \(\mathrm{AgCl}=1.8 \times 10^{-10}\) at \(298 \mathrm{~K}\). If ammonia is added to a water solution containing excess of \(\mathrm{AgCl}(\mathrm{s})\) only, calculate the concentration of the complex in \(1.0 \mathrm{M}\) aqueous ammonia.

Calculate the \(\mathrm{pH}\) of an aqueous solution of \(1.0 \mathrm{M}\) ammonium formate assuming complete dissociation. (p \(K_{a}\) of formic acid \(=3.8\) and \(\mathrm{p} K_{b}\) of ammonia \(=4.8\).)

The \(\mathrm{pH}\) of blood stream is maintained by a proper balance of \(\mathrm{H}_{2} \mathrm{CO}_{3}\) and \(\mathrm{NaHCO}_{3}\) concentrations. What volume of \(5 \mathrm{M} \mathrm{NaHCO}_{3}\) solution should be mixed with a \(10 \mathrm{~mL}\) sample of blood which is \(2 \mathrm{M}\) in \(\mathrm{H}_{2} \mathrm{CO}_{3}\) in order to maintain a \(\mathrm{pH}\) of \(7.4 ? K_{a}\) for \(\mathrm{H}_{2} \mathrm{CO}_{3}\) in blood is \(7.8 \times 10^{-7}\).

62\. For the reaction $$ \left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-} \rightleftharpoons \mathrm{Ag}^{+}+2 \mathrm{CN}^{-} $$ the equilibrium costant, at \(25^{\circ} \mathrm{C}\), is \(4.0 \times 10^{-19} .\) Calculate the silver ion concentration in a solution which was originally \(0.10\) molar in KCN and \(0.03\) molar in \(\mathrm{AgNO}_{3}\).

In the reaction \(\mathrm{I}^{-}+\mathrm{I}_{2} \rightarrow \mathrm{I}_{3}^{-}\), the Lewis acid is \(\ldots \ldots \ldots .\)

For the reaction $$ \left[\mathrm{Ag}(\mathrm{CN})_{2}\right]^{-} \rightleftharpoons \mathrm{Ag}^{+}+2 \mathrm{CN}^{-} $$ the equilibrium costant, at \(25^{\circ} \mathrm{C}\), is \(4.0 \times 10^{-19} .\) Calculate the silver ion concentration in a solution which was originally \(0.10\) molar in KCN and \(0.03\) molar in \(\mathrm{AgNO}_{3}\).