Chemical Equilibrium | JEE Main Chemistry Chapter Wise Question Papers

Q 11 :

The reaction $A(g) ⇌ B(g) + C(g)$ was initiated with the amount ' $a$ ' of $A(g)$ . At equilibrium it is found that the amount of $A(g)$ remaining is $(a - x)$ at a total pressure of $p$ . The equilibrium constant $K_{p}$ of the reaction can be calculated from the expression: [2026]

$\frac{x^{2}}{a^{2} + x^{2}} \times p$
$\frac{x^{2}}{a^{2} - x^{2}} \times p$
$\frac{a + x^{2}}{x^{2}} \times p$
$\frac{a^{2} - x^{2}}{x^{2}} \times p$

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(2)

$\begin{matrix} A (g) & ⇌ & B (g) & + & C (g) \\ t = 0 (mol) & a & 0 & 0 \\ t = \infty (mol) & a - x & x & x & total = a + x \\ t = \infty (mol fraction) & \frac{a - x}{a + x} & \frac{x}{a + x} & \frac{x}{a + x} \\ t = \infty (partial pressure) & \frac{a - x}{a + x} p & \frac{x}{a + x} p & \frac{x}{a + x} p \end{matrix}$

$K_{p} = \frac{p_{B} \times p_{C}}{p_{A}} = \frac{(\frac{x}{a + x} p) \times (\frac{x}{a + x} p)}{(\frac{a - x}{a + x} p)}$

$= \frac{x^{2} p}{(a + x) (a - x)} = \frac{x^{2} p}{a^{2} - x^{2}}$

Q 12 :

One mole each of He and A(g) are taken in a 10 L closed flask and heated to 400 K to establish the following equilibrium.

$A (g) ⇌ B (g)$

$K_{c}$ for this reaction at 400 K is 4.0. The partial pressures (in atm) of He and B(g) are respectively (at equilibrium)

(Assume He, A(g) and B(g) behave as ideal gases)

(Given: R = 0.082 L atm $K^{- 1} m o l^{- 1}$ ) [2026]

3.28, 2.624
2.624, 3.28
3.28, 0.656
0.656, 6.56

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(1)

$\begin{matrix} A (g) & ⇌ & B (g) \\ t = 0 (mol) & 1 & 0 \\ t = \infty (mol) & 1 - x & x \\ t = \infty (conc) & \frac{1 - x}{10} & \frac{x}{10} \end{matrix}$

$K_{C} = \frac{[B]}{[A]} = \frac{x / 10}{(1 - x) / 10} = \frac{x}{1 - x} = 4$

$x = 0.8$

$P_{He} = \frac{n_{He} R T}{V} = \frac{1 R T}{V} = \frac{1 \times 0.082 \times 400}{10} L = 3.28 atm$

$P_{B} = \frac{n_{B} R T}{V} = \frac{x R T}{V} = \frac{0.8 \times 0.082 \times 400}{10} L = 2.624 atm$

Q 13 :

Given is a concentrated solution of a weak electrolyte $A_{x} B_{y}$ of concentration $' c'$ and dissociation constant $' K'$ . The degree of dissociation is given by: [2026]

${[K \times c^{x + y - 1} x^{x} y^{y}]}^{x + y}$
${(\frac{K}{c^{x + y - 1} x^{x} y^{y}})}^{\frac{1}{x + y}}$
${(\frac{c^{x + y - 1} x^{x} y^{y}}{K})}^{x + y}$
${(\frac{c^{x + y - 1} x^{x} y^{y}}{K})}^{\frac{1}{x + y}}$

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(2)

$\begin{matrix} A_{x} B_{y} & ⇌ & x A^{y +} & + & y B^{x -} \\ t = 0 (conc.) & c & 0 & 0 \\ t = \infty (conc.) & c (1 - α) & x c α & y c α \end{matrix}$

$K = \frac{{[A^{y +}]}^{x} {[B^{x -}]}^{y}}{[A_{x} B_{y}]} = \frac{{(x c α)}^{x} {(y c α)}^{y}}{c (1 - α)} = \frac{x^{x} y^{y} c^{x + y - 1} α^{x + y}}{(1 - α)}$

$For a concentrated solution α ≪ 1, so 1 - α ≃ 1$

$K = x^{x} y^{y} c^{x + y - 1} α^{x + y}$

$α = {(\frac{K}{x^{x} y^{y} c^{x + y - 1}})}^{\frac{1}{x + y}}$

Q 14 :

Consider the following gas phase reaction being carried out in a closed vessel at $25 ° C$ .

$2 A (g) \to 4 B (g) + C (g)$

$\begin{matrix} time \\ (\min) \end{matrix}$ $\begin{matrix} Total pressure of the system \\ (mm Hg) \end{matrix}$

$30$ $300$

$\infty$ $600$

The pressure of $C (g)$ at 30 minutes time interval would be ___ $mm Hg$ . (nearest integer) [2026]

(20)

$\begin{array}{lcccc} 2 A(g) & \to & 4 B(g) + C(g) \\ t = 0 (pressure) & P ° & 0 0 \\ t = 30 min (pressure) & P ° - 2 p & 4 p p & P ° + 3 p = 300 \dots (i) \\ t = \infty (pressure) & 0 & 2 P ° P ° / 2 & 2.5 P ° = 600 \dots (ii) \end{array}$

From (i) and (ii)

$P ° = 240$ and $p = 20$

Pressure of $C$ at $t$ = 30 min is $p$ = 20 mmHg.

Topic Question Set

Q 11 :

The reaction $A(g) ⇌ B(g) + C(g)$ was initiated with the amount ' $a$ ' of $A(g)$ . At equilibrium it is found that the amount of $A(g)$ remaining is $(a - x)$ at a total pressure of $p$ . The equilibrium constant $K_{p}$ of the reaction can be calculated from the expression: [2026]

Q 13 :

Given is a concentrated solution of a weak electrolyte $A_{x} B_{y}$ of concentration $' c'$ and dissociation constant $' K'$ . The degree of dissociation is given by: [2026]

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$\begin{matrix} time \\ (\min) \end{matrix}$	$\begin{matrix} Total pressure of the system \\ (mm Hg) \end{matrix}$
$30$	$300$
$\infty$	$600$

Topic Question Set

Q 11 : The reaction A(g)⇌B(g)+C(g) was initiated with the amount 'a' of A(g). At equilibrium it is found that the amount of A(g) remaining is (a-x) at a total pressure of p. The equilibrium constant Kp of the reaction can be calculated from the expression: [2026]

Q 13 : Given is a concentrated solution of a weak electrolyte AxBy of concentration 'c' and dissociation constant 'K'. The degree of dissociation is given by: [2026]

Q 14 : Consider the following gas phase reaction being carried out in a closed vessel at 25°C. 2A(g)→4B(g)+C(g) time(min) Total pressure of the system(mm Hg) 30 300 ∞ 600 The pressure of C(g) at 30 minutes time interval would be ___ mm Hg. (nearest integer) [2026]

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Q 11 :

The reaction $A(g) ⇌ B(g) + C(g)$ was initiated with the amount ' $a$ ' of $A(g)$ . At equilibrium it is found that the amount of $A(g)$ remaining is $(a - x)$ at a total pressure of $p$ . The equilibrium constant $K_{p}$ of the reaction can be calculated from the expression: [2026]

Q 13 :

Given is a concentrated solution of a weak electrolyte $A_{x} B_{y}$ of concentration $' c'$ and dissociation constant $' K'$ . The degree of dissociation is given by: [2026]