Chemical & Ionic Equilibrium · JEE Main previous year questions

1. A.$\mathrm{d}q\ne 0$
2. B.The pressure in the vessel B before opening the stopcock is zero
3. C.$\mathrm{d}w\ne 0$
4. D.$\mathrm{dU}\ne 0$

1. A.$p>q>r>s$
2. B.$r>q>p>s$
3. C.$p>r>q>s$
4. D.$q>p>r>s$

Consider the following chemical equilibrium of the gas phase reaction at a constant temperature : $\mathrm{A}(\mathrm{g})\rightleftharpoons \mathrm{B}(\mathrm{g})+\mathrm{C}(\mathrm{g})$ If $p$ being the total pressure, $K_p$ is the pressure equilibrium constant and $\alpha$ is the degree of dissociation, then which of the following is true at equilibrium?

1. A.If $K_p$ value is extremely high compared to $p$, $\alpha$ becomes much less than unity
2. B.When p increases $\alpha$ increases
3. C.If p value is extremely high compared to ${\mathrm{K}}_{\mathrm{p}}$, $\alpha \approx 1$
4. D.When $p$ increases $\alpha$ decreases

Consider the equilibrium $$\mathrm{CO}(\mathrm{g})+3{\mathrm{H}}_2(\mathrm{g})\rightleftharpoons \mathrm{C}{\mathrm{H}}_4(\mathrm{g})+{\mathrm{H}}_2\mathrm{O}(\mathrm{g})$$ If the pressure applied over the system increases by two fold at constant temperature then (A) Concentration of reactants and products increases. (B) Equilibrium will shift in forward direction. (C) Equilibrium constant increases since concentration of products increases. (D) Equilibrium constant remains unchanged as concentration of reactants and products remain same. Choose the correct answer from the options given below :

1. A.(A) and (B) only
2. B.(A), (B) and (D) only
3. C.(B) and (C) only
4. D.(A), (B) and (C) only

A weak acid HA has degree of dissociation $x$. Which option gives the correct expression of $(\mathrm{pH}-\mathrm{p}{\mathrm{K}}_{\mathrm{a}})$?

1. A.$\log \left(\frac{1-x}{x}\right)$
2. B.$0$
3. C.$\log (1+2x)$
4. D.$\log \left(\frac{x}{1-x}\right)$

Given below are two statements: Statement I: In the oxalic acid vs $\mathrm{KMn}{\mathrm{O}}_4$ (in the presence of dil ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$ ) titration the solution needs to be heated initially to $60^{\circ }\mathrm{C}$, but no heating is required in Ferrous ammonium sulphate (FAS) vs $\mathrm{KMn}{\mathrm{O}}_4$ titration (in the presence of dil ${\mathrm{H}}_2\mathrm{S}{\mathrm{O}}_4$) Statement II: In oxalic acid vs $\mathrm{KMn}{\mathrm{O}}_4$ titration, the initial formation of $\mathrm{MnS}{\mathrm{O}}_4$ takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs $\mathrm{KMn}{\mathrm{O}}_4$, heating oxidizes $\mathrm{F}{\mathrm{e}}^{2+}$ into $\mathrm{F}{\mathrm{e}}^{3+}$ by oxygen of air and error may be introduced in the experiment. In the light of the above statements, choose the correct answer from the options given below

1. A.Statement I is false but Statement II is true
2. B.Statement I is true but Statement II is false
3. C.Both Statement I and Statement II are true
4. D.Both Statement I and Statement II are false

${\mathrm{K}}_{\mathrm{sp}}$ for $\mathrm{Cr}(\mathrm{OH}{)}_3$ is $1.6\times 10^{-30}$. What is the molar solubility of this salt in water?

1. A.$\sqrt[5]{1.8\times 10^{-30}}$
2. B.$\frac{1.8\times 10^{-30}}{27}$
3. C.$\sqrt[4]{\frac{1.6\times 10^{-30}}{27}}$
4. D.$\sqrt[2]{1.6\times 10^{-30}}$

$37.8\mathrm{g}{\mathrm{N}}_2{\mathrm{O}}_5$ was taken in a $1\mathrm{L}$ reaction vessel and allowed to undergo the following reaction at $500\mathrm{K}$ $2{\mathrm{N}}_2{\mathrm{O}}_{5(\mathrm{g})}\rightleftharpoons 2{\mathrm{N}}_2{\mathrm{O}}_{4(\mathrm{g})}+{\mathrm{O}}_{2(\mathrm{g})}$ The total pressure at equilibrium was found to be $18.65\mathrm{bar}$. Then, $\mathrm{Kp}=$ ____ $\times 10^{-2}$ [nearest integer] Assume ${\mathrm{N}}_2{\mathrm{O}}_5$ to behave ideally under these conditions. Given: $\mathrm{R}=0.082\mathrm{bar}\mathrm{Lmo}{\mathrm{l}}^{-1}{\mathrm{K}}^{-1}$

Standard entropies of ${\mathrm{X}}_2$, ${\mathrm{Y}}_2$ and $\mathrm{X}{\mathrm{Y}}_5$ are $70$, $50$ and $110\mathrm{J}{\mathrm{K}}^{-1}\mathrm{mo}{\mathrm{l}}^{-1}$ respectively. The temperature in Kelvin at which the reaction $\frac{1}{2}{\mathrm{X}}_2+\frac{5}{2}{\mathrm{Y}}_2\rightleftharpoons \mathrm{X}{\mathrm{Y}}_5\Delta {\mathrm{H}}^{\ominus }=-35\mathrm{kJ}\mathrm{mo}{\mathrm{l}}^{-1}$ will be at equilibrium is ____ (Nearest integer)

1. A.
2. B.
3. C.
4. D.

$\mathrm{pH}$ of water is 7 at $25^{\circ }\mathrm{C}$. If water is heated to $80^{\circ }\mathrm{C}$., it's $\mathrm{pH}$ will :

1. A.Decrease
2. B.Remains the same
3. C.Increase
4. D.${\mathrm{H}}^{+}$concentration increases, ${\mathrm{OH}}^{-}$concentration decreases

Consider the reaction ${\mathrm{X}}_2\mathrm{Y}(\mathrm{g})\rightleftharpoons {\mathrm{X}}_2(\mathrm{g})+\frac{1}{2}{\mathrm{Y}}_2(\mathrm{g})$ The equation representing correct relationship between the degree of dissociation (x) of ${\mathrm{X}}_2\mathrm{Y}(\mathrm{g})$ with its equilibrium constant Kp is ____. Assume $x$ to be very very small.

1. A.$x=\sqrt[3]{\frac{\mathrm{Kp}}{\mathrm{p}}}$
2. B.$x=\sqrt[3]{\frac{\mathrm{Kp}}{2\mathrm{p}}}$
3. C.$x=\sqrt[3]{\frac{2{\mathrm{Kp}}^2}{\mathrm{p}}}$
4. D.$x=\sqrt[3]{\frac{2\mathrm{Kp}}{\mathrm{p}}}$

A vessel at $1000\text{ K}$ contains ${\mathrm{CO}}_2$ with a pressure of $0.5\text{ atm}$ . Some of ${\mathrm{CO}}_2$ is converted into $\mathrm{CO}$ on addition of graphite. If total pressure at equilibrium is $0.8\text{ atm}$ , then ${\mathrm{K}}_{\mathrm{p}}$ is :

1. A.$0.18\text{ atm}$
2. B.$0.3\text{ atm}$
3. C.$3\text{ atm}$
4. D.$1.8\text{ atm}$

1. A.Pyridine > Piperidine > Pyrrole
2. B.Pyrrole > Piperidine > Pyridine
3. C.Pyrrole > Pyridine > Piperidine
4. D.Piperidine > Pyridine > Pyrrole

1. A.
2. B.
3. C.
4. D.

For a sparingly soluble salt $\mathrm{A}{\mathrm{B}}_2$, the equilibrium concentrations of ${\mathrm{A}}^{2+}$ ions and $B^{-}$ ions are $1.2\times 10^{-4}\mathrm{M}$ and $0.24\times 10^{-3}\mathrm{M}$, respectively. The solubility product of $\mathrm{A}{\mathrm{B}}_2$ is :

1. A.$0.069\times 10^{-12}$
2. B.$0.276\times 10^{-12}$
3. C.$6.91\times 10^{-12}$
4. D.$27.65\times 10^{-12}$

For the given hypothetical reactions, the equilibrium constants are as follows : $\mathrm{X}\rightleftharpoons \mathrm{Y};{\mathrm{K}}_1=1.0$ $\mathrm{Y}\rightleftharpoons \mathrm{Z};{\mathrm{K}}_2=2.0$ $\mathrm{Z}\rightleftharpoons \mathrm{W};{\mathrm{K}}_3=4.0$ The equilibrium constant for the reaction $\mathrm{X}\rightleftharpoons \mathrm{W}$ is

1. A.12.0
2. B.8.0
3. C.6.0
4. D.7.0

Given below are two statements : Statement (I) : A Buffer solution is the mixture of a salt and an acid or a base mixed in any particular quantities Statement (II) : Blood is a naturally occurring buffer solution whose $\mathrm{pH}$ is maintained by ${\mathrm{H}}_2\mathrm{C}{\mathrm{O}}_3/HC{\mathrm{O}}_3^{\ominus }$ concentrations. In the light of the above statements, choose the correct answer from the options given below :

1. A.Both Statement I and Statement II are false
2. B.Both Statement I and Statement II are true
3. C.Statement I is false but Statement II is true
4. D.Statement I is true but Statement II is false

The equilibrium $\mathrm{C}{\mathrm{r}}_2{\mathrm{O}}_7^{2-}\rightleftharpoons 2\mathrm{Cr}{\mathrm{O}}_4^{2-}$ is shifted to the right in :

1. A.a weakly acidic medium
2. B.a basic medium
3. C.a neutral medium
4. D.an acidic medium

Given below are two statements : Statement I : On passing ${\mathrm{HCl}}_{(g)}$ through a saturated solution of ${\mathrm{BaCl}}_2$, at room temperature white turbidity appears. Statement II : When $\mathrm{HCl}$ gas is passed through a saturated solution of $\mathrm{NaCl}$, sodium chloride is precipitated due to common ion effect. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Both Statement I and Statement II are correct
2. B.Statement I is incorrect but Statement II is correct
3. C.Both Statement I and Statement II are incorrect
4. D.Statement I is correct but Statement II is incorrect

What will be the decreasing order of basic strength of the following conjugate bases? ${}^{-}\mathrm{OH},\mathrm{R}\overline{\mathrm{O}},\mathrm{C}{\mathrm{H}}_3\mathrm{CO}\overline{\mathrm{O}},{\mathrm{Cl}}^{-}$

1. A.${\mathrm{Cl}}^{-}>\mathrm{R}\overline{\mathrm{O}}>{}^{-}\mathrm{OH}>\mathrm{C}{\mathrm{H}}_3\mathrm{CO}\overline{\mathrm{O}}$
2. B.${}^{-}\mathrm{OH}>\mathrm{R}\overline{\mathrm{O}}>\mathrm{C}{\mathrm{H}}_3\mathrm{CO}\overline{\mathrm{O}}>{\mathrm{Cl}}^{-}$
3. C.${\mathrm{Cl}}^{-}>{}^{-}\mathrm{OH}>\mathrm{R}\overline{\mathrm{O}}>\mathrm{C}{\mathrm{H}}_3\mathrm{CO}\overline{\mathrm{O}}$
4. D.$\mathrm{R}\overline{\mathrm{O}}>{}^{-}\mathrm{OH}>\mathrm{C}{\mathrm{H}}_3\mathrm{CO}\overline{\mathrm{O}}>{\mathrm{Cl}}^{-}$

The equilibrium constant for the reaction ${\text{SO}}_3(\text{g})\rightleftharpoons {\text{SO}}_2(\text{g})+\frac{1}{2}{\text{O}}_2(\text{g})$ is ${\text{K}}_c=4.9\times 10^{-2}$. The value of ${\text{K}}_c$ for the reaction given below $2{\text{SO}}_2(\text{g})+{\text{O}}_2(\text{g})\rightleftharpoons 2{\text{SO}}_3(\text{g})$ is :

1. A.49
2. B.416
3. C.41.6
4. D.4.9

Given below are two statements : Statement (I) : Potassium hydrogen phthalate is a primary standard for standardisation of sodium hydroxide solution. Statement (II) : In this titration phenolphthalein can be used as indicator. In the light of the above statements, choose the most appropriate answer from the options given below :

1. A.Both Statement I and Statement II are correct
2. B.Statement I is incorrect but Statement II is correct
3. C.Both Statement I and Statement II are incorrect
4. D.Statement I is correct but Statement II is incorrect

${\mathrm{K}}_{\mathrm{a}}$ for $\mathrm{C}{\mathrm{H}}_3\mathrm{COOH}$ is $1.8\times 10^{-5}$ and ${\mathrm{K}}_{\mathrm{b}}$ for $\mathrm{N}{\mathrm{H}}_4\mathrm{OH}$ is $1.8\times 10^{-5}$. The $\mathrm{pH}$ of ammonium acetate solution will be ________ .

Solubility of calcium phosphate (molecular mass, $\mathrm{M}$) in water is ${\mathrm{W}}_{\mathrm{g}}$ per $100\text{ mL}$ at $25^{\circ }\text{C}$. Its solubility product at $25^{\circ }\text{C}$ will be approximately.

1. A.$10^7{\left(\frac{\mathrm{W}}{\mathrm{M}}\right)}^3$
2. B.$10^3{\left(\frac{\mathrm{W}}{\mathrm{M}}\right)}^5$
3. C.$10^7{\left(\frac{\mathrm{W}}{\mathrm{M}}\right)}^5$
4. D.$10^5{\left(\frac{\mathrm{W}}{\mathrm{M}}\right)}^5$