Chemical & Ionic Equilibrium · JEE Main previous year questions

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2025 23 questions

Q702025 · 8 Apr 2025 · Shift 2
1. A.
2. B.
3. C.
4. D.
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Answer: C
Q712025 · 8 Apr 2025 · Shift 2· Numerical answer
Consider the following half cell reaction $C r_{2} O_{7}^{2 -} (aq) + 6 e^{-} + 14 H^{+} (aq) \to 2C r^{3 +} (aq) + 7 H_{2} O (ℓ)$ The reaction was conducted with the ratio of $\frac{[ Cr ^{3 +} ] ^{2}}{[ Cr _{2} O _{7}^{2 -} ]} = 1 0^{- 6}$ . The pH value at which the EMF of the half cell will become zero is ____ . (nearest integer value) $[Given: standard half cell reduction potential E_{C r_{2} O_{7}^{2 -}, H^{+} /C r^{3 +}}^{\circ} = 1.33 V, \frac{2.303 R T}{F} = 0.059 V.]$
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Answer: 10
Q732025 · 8 Apr 2025 · Shift 2· Numerical answer
The equilibrium constant for decomposition of $H_{2} O (g)$ $H_{2} O (g) ⇌ H_{2} (g) + \frac{1}{2} O_{2} (g) (Δ G^{\circ} = 92.34 kJ mo l^{- 1})$ is $8.0 \times 1 0^{- 3}$ at $2300 K$ and total pressure at equilibrium is 1 bar. Under this condition, the degree of dissociation $(α)$ of water is ____ $\times 1 0^{- 2}$ (nearest integer value). [Assume $α$ is negligible with respect to 1]
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Answer: 5
Q712025 · 4 Apr 2025 · Shift 1· Numerical answer
The pH of a 0.01 M weak acid HX ( $K_{a} = 4 \times 1 0^{- 10}$ ) is found to be 5 . Now the acid solution is diluted with excess of water so that the pH of the solution changes to 6 . The new concentration of the diluted weak acid is given as $x \times 1 0^{- 4} M$ . The value of $x$ is ____ (nearest integer)
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Answer: 25
Q742025 · 4 Apr 2025 · Shift 2· Numerical answer
The molar conductance of an infinitely dilute solution of ammonium chloride was found to be $185 S cm^{2} mol^{- 1}$ and the ionic conductance of hydroxyl and chloride ions are $170$ and $70 S cm^{2} mol^{- 1}$ , respectively. If molar conductance of $0.02 M$ solution of ammonium hydroxide is $85.5 S cm^{2} mol^{- 1}$ , its degree of dissociation is given by $x \times 1 0^{- 1}$ . The value of $x$ is . (Nearest integer)
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Answer: 3
Q752025 · 4 Apr 2025 · Shift 2· Numerical answer
$x mg$ of $Mg (OH)_{2} (molar mass = 58)$ is required to be dissolved in $1.0 L$ of water to produce a $pH$ of $10.0$ at $298 K$ . The value of $x$ is $mg$ . (Nearest integer) (Given : $Mg (OH)_{2}$ is assumed to dissociate completely in $H_{2} O$ )
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Answer: 3
Q562025 · 3 Apr 2025 · Shift 1
In the following system, $PC l_{5} (g) ⇌ PC l_{3} (g) + C l_{2} (g)$ at equilibrium, upon addition of xenon gas at constant $T$ and $p$ , the concentration of
1. A. $PC l_{5}$ , $PC l_{3}$ and $C l_{2}$ remain constant
2. B. $PC l_{3}$ will increase
3. C. $C l_{2}$ will decrease
4. D. $PC l_{5}$ will increase
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Answer: C
Q672025 · 3 Apr 2025 · Shift 1
Given below are two statements : Statement I : A catalyst cannot alter the equilibrium constant ( $K_{c}$ ) of the reaction, temperature remaining constant. Statement II : A homogeneous catalyst can change the equilibrium composition of a system, temperature remaining constant. In the light of the above statements, choose the correct answer from the options given below
1. A.Statement I is true but Statement II is false
2. B.Statement I is false but Statement II is true
3. C.Both Statement I and Statement II are true
4. D.Both Statement I and Statement II are false
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Answer: A
Q552025 · 3 Apr 2025 · Shift 2
Given below are two statements: Statement I : When a system containing ice in equilibrium with water (liquid) is heated, heat is absorbed by the system and there is no change in the temperature of the system until whole ice gets melted. Statement II : At melting point of ice, there is absorption of heat in order to overcome intermolecular forces of attraction within the molecules of water in ice and kinetic energy of molecules is not increased at melting point. 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.Statement I is true but Statement II is false
3. C.Both Statement I and Statement II are true
4. D.Statement I is false but Statement II is true
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Answer: C
Q532025 · 2 Apr 2025 · Shift 1
If equal volumes of $A B_{2}$ and $X Y$ (both are salts) aqueous solutions are mixed, which of the following combination will give a precipitate of $A Y_{2}$ at $300 K$ ? (Given $K_{sp}$ ( at $300 K$ ) for $A Y_{2} = 5.2 \times 1 0^{- 7}$ )
1. A. $2.0 \times 1 0^{- 4} M A B_{2}, 0.8 \times 1 0^{- 3} M X Y$
2. B. $2.0 \times 1 0^{- 2} M A B_{2}, 2.0 \times 1 0^{- 2} M X Y$
3. C. $1.5 \times 1 0^{- 4} M A B_{2}, 1.5 \times 1 0^{- 3} M X Y$
4. D. $3.6 \times 1 0^{- 3} M A B_{2}, 5.0 \times 1 0^{- 4} M X Y$
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Answer: B
Q632025 · 2 Apr 2025 · Shift 1
1. A. $d q \neq = 0$
2. B.The pressure in the vessel B before opening the stopcock is zero
3. C. $d w \neq = 0$
4. D. $dU \neq = 0$
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Answer: B
Q702025 · 2 Apr 2025 · Shift 1
1. A. $p > q > r > s$
2. B. $r > q > p > s$
3. C. $p > r > q > s$
4. D. $q > p > r > s$
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Answer: A
Q702025 · 2 Apr 2025 · Shift 2
Consider the following chemical equilibrium of the gas phase reaction at a constant temperature : $A (g) ⇌ B (g) + C (g)$ If $p$ being the total pressure, $K_{p}$ is the pressure equilibrium constant and $α$ 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 $p$ , $α$ becomes much less than unity
2. B.When p increases $α$ increases
3. C.If p value is extremely high compared to $K_{p}$ , $α \approx 1$
4. D.When $p$ increases $α$ decreases
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Answer: D
Q622025 · 29 Jan 2025 · Shift 2
Consider the equilibrium $CO (g) + 3 H_{2} (g) ⇌ C H_{4} (g) + H_{2} O (g)$ 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
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Answer: A
Q542025 · 28 Jan 2025 · Shift 1
A weak acid HA has degree of dissociation $x$ . Which option gives the correct expression of $(pH - p K_{a})$ ?
1. A. $lo g (\frac{1 - x}{x})$
2. B. $0$
3. C. $lo g (1 + 2 x)$
4. D. $lo g (\frac{x}{1 - x})$
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Answer: D
Q592025 · 28 Jan 2025 · Shift 1
Given below are two statements: Statement I: In the oxalic acid vs $KMn O_{4}$ (in the presence of dil $H_{2} S O_{4}$ ) titration the solution needs to be heated initially to $6 0^{\circ} C$ , but no heating is required in Ferrous ammonium sulphate (FAS) vs $KMn O_{4}$ titration (in the presence of dil $H_{2} S O_{4}$ ) Statement II: In oxalic acid vs $KMn O_{4}$ titration, the initial formation of $MnS O_{4}$ takes place at high temperature, which then acts as catalyst for further reaction. In the case of FAS vs $KMn O_{4}$ , heating oxidizes $F e^{2 +}$ into $F e^{3 +}$ 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
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Answer: C
Q592025 · 24 Jan 2025 · Shift 1
$K_{sp}$ for $Cr (OH)_{3}$ is $1.6 \times 1 0^{- 30}$ . What is the molar solubility of this salt in water?
1. A. $5 1.8 \times 1 0^{- 30}$
2. B. $\frac{1.8 \times 1 0 ^{- 30}}{27}$
3. C. $4 \frac{1.6 \times 1 0 ^{- 30}}{27}$
4. D. $2 1.6 \times 1 0^{- 30}$
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Answer: C
Q712025 · 24 Jan 2025 · Shift 1· Numerical answer
$37.8 g N_{2} O_{5}$ was taken in a $1 L$ reaction vessel and allowed to undergo the following reaction at $500 K$ $2 N_{2} O_{5 (g)} ⇌ 2 N_{2} O_{4 (g)} + O_{2 (g)}$ The total pressure at equilibrium was found to be $18.65 bar$ . Then, $Kp =$ ____ $\times 1 0^{- 2}$ [nearest integer] Assume $N_{2} O_{5}$ to behave ideally under these conditions. Given: $R = 0.082 bar Lmo l^{- 1} K^{- 1}$
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Answer: 962
Q752025 · 24 Jan 2025 · Shift 1· Numerical answer
Standard entropies of $X_{2}$ , $Y_{2}$ and $X Y_{5}$ are $70$ , $50$ and $110 J K^{- 1} mo l^{- 1}$ respectively. The temperature in Kelvin at which the reaction $\frac{1}{2} X_{2} + \frac{5}{2} Y_{2} ⇌ X Y_{5} Δ H^{⊖} = - 35 kJ mo l^{- 1}$ will be at equilibrium is ____ (Nearest integer)
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Answer: 700
Q642025 · 24 Jan 2025 · Shift 2
1. A.
2. B.
3. C.
4. D.
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Answer: C
Q512025 · 23 Jan 2025 · Shift 2
$pH$ of water is 7 at $2 5^{\circ} C$ . If water is heated to $8 0^{\circ} C$ ., it's $pH$ will :
1. A.Decrease
2. B.Remains the same
3. C.Increase
4. D. $H^{+}$ concentration increases, $OH^{-}$ concentration decreases
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Answer: A
Q652025 · 23 Jan 2025 · Shift 2
Consider the reaction $X_{2} Y (g) ⇌ X_{2} (g) + \frac{1}{2} Y_{2} (g)$ The equation representing correct relationship between the degree of dissociation (x) of $X_{2} Y (g)$ with its equilibrium constant Kp is ____. Assume $x$ to be very very small.
1. A. $x = 3 \frac{Kp}{p}$
2. B. $x = 3 \frac{Kp}{2 p}$
3. C. $x = 3 \frac{2 Kp ^{2}}{p}$
4. D. $x = 3 \frac{2 Kp}{p}$
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Answer: C
Q572025 · 22 Jan 2025 · Shift 1
A vessel at $1000 K$ contains $CO_{2}$ with a pressure of $0.5 atm$ . Some of $CO_{2}$ is converted into $CO$ on addition of graphite. If total pressure at equilibrium is $0.8 atm$ , then $K_{p}$ is :
1. A. $0.18 atm$
2. B. $0.3 atm$
3. C. $3 atm$
4. D. $1.8 atm$
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Answer: D