HARD

Earn 100

Hemoglobin $(Hb)$ protein transport $O_{2}$ in blood and each $Hb$ can bind $4 O_{2}$ , molecules. In discussing protein oxygen binding capacity, biochemists use a measure called the $P^{50}$ value, defined as the partial pressure of oxygen at which $50 %$ of hemoglobin is saturated. Fetal hemoglobin has a $P^{50}$ value of $20$ torr and adult has $P^{50}$ value of $40$ torr. For the following equilibrium:

$4 O_{2} (g) + Hb (aq) \to [Hb {(O_{2})}_{4} (aq)]$

What is the value of $K_{fetal} / K_{adult} ?$

[Where $K$ represents equilibrium constant.]

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Important Questions on Equilibrium

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The standard Gibbs energy change at 300 K for the reaction

2 A ⇌ B + C

is 2494.2 J. At a given time, the composition of the reaction mixture is

[A] = \frac{1}{2}, [B] = 2

and

[C] = \frac{1}{2}

. The reaction proceeds in the:

[R = 8.314 J / K - m o l, e = 2.718]

{Given antilog (-0.44)=0.36}

EASY

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The reaction

C_{2} H_{6} (g) ⇌ C_{2} H_{4} (g) + H_{2} (g)

is at equilibrium in a closed vessel at 1000 K. The enthalpy change

(∆ H)

for the reaction is

137.0 k J m o l^{- 1}

. Which one of the following actions would shift the equilibrium to the right?

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The percentage of pyridine

(C_{5} H_{5} N)

that forms pyridinium ion

(C_{5} H_{5} N^{+} H)

in a

0.10 M

aqueous pyridine solution

(K_{b} for C_{5} H_{5} N = 1 .7 \times 10^{- 9})

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Consider the equilibrium

X_{2} + Y_{2} ⇌ P

. Find the stoichiometric coefficient of the

P

using the data given in the following table:

$X_{2} / m o l L^{- 1}$	$Y_{2} / m o l L^{- 1}$	$P / m o l L^{- 1}$
$1.14 \times 10^{- 2}$	$0.12 \times 10^{- 2}$	$2.52 \times 10^{- 2}$
$0.92 \times 10^{- 2}$	$0.22 \times 10^{- 2}$	$3.08 \times 10^{- 2}$

EASY

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Consider the following reversible chemical reactions:

A_{2} (g) + B_{2} (g) \overset{k_{1}}{⇌} 2 A B (g)

.....(1)

6 A B (g) \overset{k_{2}}{⇌} 3 A_{2} (g) + 3 B_{2} (g)

.....(2)

The relation between

K_{1}

and

K_{2}

is:

EASY

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Of the following reactions

(i)

A ⇌ B, ∆ G^{o} = 250 kJ {mol}^{- 1}

(ii)

D ⇌ E, ∆ G^{o} = - 100 kJ {mol}^{- 1}

(iii)

F ⇌ G, ∆ G^{o} = - 150 kJ {mol}^{- 1}

(iv)

M ⇌ N, ∆ G^{o} = 150 kJ {mol}^{- 1}

The reaction with the largest equilibrium constant is

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Which of the following statements is correct for a reversible process in the state of equilibrium?

EASY

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The equilibrium constants for the reactions

X ⇋ 2 Y

and

Z ⇋ P + Q

are

K_{1}

and

K_{2},

respectively. If the initial concentrations and the degree of dissociation of

X

and

Z

are the same, the ratio

K_{1} / K_{2}

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

5 .1 g {NH}_{4} SH

is introduced in

3 .0 L

evacuated flask at

327^{o} C

30 %

of the solid

{NH}_{4} SH

is decomposed to

{NH}_{3}

and

H_{2} S

as gases. The

K_{P}

of the reaction at

327^{o} C

(R = 0 .082 L atm {mol}^{- 1} K^{- 1}, Molar mass of S = 32 g {mol}^{- 1}, Molar mass of N = 14 g {mol}^{- 1})

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Consider an electrochemical cell:

A (s) |A^{n +} (aq, 2 M)| |B^{2 n +} (aq, 1 M)| B (s)

. The value of

{ΔH}^{o}

for the cell reaction is twice that of

{ΔG}^{o}

300 K .

If the emf of the cell is zero, the magnitude of

Δ S^{o}

(in {JK}^{- 1} {mol}^{- 1})

of the cell reaction per mole of

B

formed at

300 K

is ____

{Jmol}^{- 1} K^{- 1}

. (Give answer after rounding off to the nearest integer value.)
(Given: R

= 8.3 {JK}^{- 1} {mol}^{- 1} .

H, S

and

G

are enthalpy, entropy and Gibbs energy, respectively.)

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

For the reaction,

A ⇌ n B

the concentration of A decreases from

0.06 t o 0.03 m o l L^{- 1}

and that of B rises from

0 t o 0.06 m o l L^{- 1}

at equilibrium. The values of n and the equilibrium constant for the reaction, respectively, are

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

In a chemical reaction,

A + 2 B \overset{K}{⇌} 2 C + D

, the initial concentration of

B

was

1.5

times of the concentration of

A

, but the equilibrium concentrations of

A

and

B

were found to be equal. The equilibrium constant

(K)

for the chemical reaction is:

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

20 litre

container at

400 K

contains

{CO}_{2} (g)

at pressure

0.4 atm

and an excess of

SrO

(neglect the volume of solid

SrO

). The volume of the container is now decreased by moving the movable piston fitted in the container. The maximum volume of the container, when the pressure of

{CO}_{2}

attains its maximum value, will be:

(Given that : {SrCO}_{3} (s) ⇌ SrO (s) + {CO}_{2} (g), K_{p} = 1 .6 atm)

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

At 320 K, a gas

A_{2}

is 20 % dissociated to

A (g)

. The standard Gibbs free energy change at

320 K a n d 1 a t m i n J m o l^{- 1}

is approximately:

(R = 8 .314 {JK}^{- 1} {mol}^{- 1}; \ln 2 = 0 .693; \ln 3 = 1 .098)

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The equilibrium constants of the following are:

\begin{matrix} N_{2} + 3 H_{2} ⇌ 2 {NH}_{3} & K_{1} \\ N_{2} + O_{2} ⇌ 2 NO & K_{2} \\ H_{2} + \frac{1}{2} O_{2} \to H_{2} O & K_{3} \end{matrix}

The equilibrium constant (

K

) of the reaction:

2 N H_{3} + \frac{5}{2} O_{2} \overset{K}{⇌} 2 N O + 3 H_{2} O

, will be:

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Consider the equilibria

(i) a n d (i i)

with equilibrium constants

K_{1} a n d K_{2}

, respectively

{SO}_{2} (g) + \frac{1}{2} O_{2} (g) ⇌ {SO}_{3} (g)

.... (i)

2 {SO}_{3} (g) ⇌ 2 {SO}_{2} (g) + O_{2} (g)

.... (ii)

K_{1} a n d K_{2}

are related as

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

The equilibrium constant

K_{c}

of the reaction,

2 A ⇌ B + C is 0 .5 at 25^{o}

and

1 atm

. The reaction will proceed in the backward direction when concentrations

[A], [B] and [C]

are, respectively -

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Gaseous

N_{2} O_{4}

dissociates into gaseous

N O_{2}

according to the reaction

N_{2} O_{4} (g) ⇌ 2 N O_{2} (g)

300 K

and

1 atm

pressure, the degree of dissociation of

N_{2} O_{4}

0.2

. If one mole of

N_{2} O_{4}

gas is contained in a vessel, then the density of the equilibrium mixture is

:

HARD

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

What are the values of

\frac{K_{p}}{K_{c}}

for the following reactions at

300 K

respectively?

(At

300 K, RT = 24 .62 {dm}^{3} atm {mol}^{- 1}

)

N_{2} (g) + O_{2} (g) ⇌ 2 NO (g); \frac{K_{p}}{K_{c}} = x_{1}

N_{2} O_{4} (g) ⇌ 2 {NO}_{2} (g); \frac{K_{p}}{K_{c}} = x_{2}

N_{2} (g) + 3 H_{2} (g) ⇌ 2 {NH}_{3} (g); \frac{K_{p}}{K_{c}} = x_{3}

MEDIUM

Chemistry>Physical Chemistry>Equilibrium>Equilibrium Constants and its Significance

Consider the nitration of benzene using mixed conc.

H_{2} S O_{4}

and

H N O_{3}

. If a large amount of

K H S O_{4}

is added to the mixture, the rate of nitration will be:

Important Questions on Equilibrium

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