A Matrix-Match Type
This section contains 2 questions. Each question contains statements given in two column which have to be matched. Statements (A, B, C, D) in Column I have to be matched with statements (p, q, r, s) in Column II. The answers to these questions have to be appropriately bubbles as illustrated in the following example.
If the correct matches are A–p, A–s, B–q, B–r, C–p, C–q and D–s, then the correctly bubbled 4 × 4 matrix should be as follows :
p q r s
1. Match the chemical reaction in equilibrium (in List I) with the pressure dependent of degree of dissociation of the reaction (in List II):
SECTION – V Comprehension Type Questions
Write-up IFor the reaction CaCO3(s) CaO(s) + CO2(g), KP(1000 K) = 0.059 and KP (1100 K)
= 0.08. Exactly 10 g of CaCO3 is placed in a 10 litre container at 1000 K. The equilibrium is reached. Assume that air contains 10% by volume of CO2.
1. The mass of CaCO3 remain unreacted at 1000 K is (a) 1.485 g (b) 0.325 g (c) 9.282 g (d) 4.56 g
2. The ratio of degree of dissociation of CaCO3 at 1110° K and 1000 K is (a) 4.256 (b) 1.356
(c) 5.286 (d) 3.456
3. The temperature at which CaCO3 dissociates freely in air is (a) 415°C (b) 913.2°C
(c) 8.05. 4°C (d) 43°C 4. The value of H is
(a) 6699 cal (b) 2399 cal
(c) 4599 cal (d) 2499 cal
Write-up IIComprehension - IILife at high attitudes and hemoglobin production: In the human body, countless chemical equilibria must be maintained to ensure physiological well being. Transport of oxygen by blood depends on the reversible combination of oxygen with haemoglobin. In blood, haemoglobin, oxygen and oxyhaemoglobin are in equilibrium.
2 2
haemoglobin (Hb) + O ‡ ˆ ˆˆ ˆ † Oxyhaemoglobin [Hb(O )]
The equilibrium constant is, c 2 2
[Hb(O )]
K [Hb][O ]
The pH of blood stream is maintained by a proper balance of H2CO3 and NaHCO3
concentrations.
According to Henderson’s equation a
[salt]
pH log K log [acid]
An important component of blood is the buffer combination of H PO2 4 ion and the HPO4 ion. Consider blood with a pH of 7.44. Given Ka1 6.9 10 3, Ka2 6.2 10 8 and Ka3 4.8 10 13.
5. What volume of 5M NaHCO3 solution should be mixed with a 10 mL sample of blood which is 2M in H2CO3, in order to maintain a pH of 7.47? Ka for H2CO3 in blood is 7.8 × 10–7 .
(a) 78.32 mL (b) 92.08 mL (c) 68.32 mL (d) None 6. What is the ratio of 2 24
4
[H PO ] [HPO ]
?
(a) 0.59 (b) 0.69 (c) 0.79 (d) None
7. What will be the pH, when 25% of the HPO24 ions are converted to H PO2 24 ion?
(a) 7.16 (b) 8.16 (c) 9.16 (d) None
8. What will be the pH, when 15% of the H PO2 4 ions are converted to HPO4 ions?
(c) 9.55 (d) None
Write-up IIIComprehension - IIILet G° be the difference in free energy of the reaction when all the reactants and products are in the standard state (1 atmospheric pressure and 298K) and KC and KP be the thermodynamic equilibrium constant of the reaction. Both are related to each other at temperature T by the following relation:
G° = –2.303 RT log KC
and G° = –2.303 RT log KP (incase of ideal gas)
This equation represents one of the most important results of thermodynamics and relates to the equilibrium constant of a reaction to a thermodynamic property.
It is sometimes easier to calculate the free energy in a reaction rather than to measure the equilibrium constant.
Standard free energy change can be thermodynamically calculated as G° = H° –TS°
Here H° = standard enthalpy change S° = standard entropy change.
9. Which of the following statement is correct for a reversible process in state of equilibrium
(a) G = –2.303 RT log K (b) G = 2.303 RT log K (c) G° = –2.303 RT log K (d) G° = 2.303 RT log K 10. At 490°C, the value of equilibrium constant; KP is 45.9 the reaction H2(g) + I2(g) ˆ ˆ†‡ ˆˆ 2HI(g)
(a) –3.5 kcal (b) 3.5 kcal (c) 5.79 kcal (d) –5.79 kcal
11. Calculate the equilibrium concentration ratio of C to A if 2.0 mol each of A and B were allowed to come to equilibrium at 300 K
A + B ‡ ˆˆˆ ˆ† C + D G° = 460 Cal (a) 1.0 (b) 0.5
(c) 0.8 (d) 0.679
C Assertion and Reasoning
This section contains 4 questions numbered 1 to 4. Each question contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason). Each question has 4 choices (A), (B), (C) and (D) out of which ONLY ONE is correct.
Code
(A) Statement – 1 is True, Statement – 2 is True; Statement – 2 is a correct explanation for Statement – 1.
(B) Statement – 1 is True, Statement – 2 is True; Statement – 2 is NOT a correct explanation for Statement – 1.
(C) Statement – 1 is True, Statement – 2 is False.
(D) Statement – 1 is False, Statement – 2 is True.
1. STATEMENT - 1
If Kp value for CaCO3(s)‡ ˆˆˆ ˆ† CaO3CO2(g) be 8 atm at 500K, the final pressure developed in 10 litre vessel on heating 50g of CaCO3(s) by enclosing in vessel at 500K will be 8 atm.
STATEMENT - 2
This amount of calcium carbonate is insufficient to establish equilibrium under given set of condition.
2. STATEMENT - 1
The positive catalyst enhances the rate of equilibrium reaction, but does not change the value of equilibrium constant at constant temperature.
STATEMENT - 2
Because the catalyst increases the value Kf and Kb in the same proportion at constant temperature.
3. STATEMENT - 1
Increasing the pressure formation of NH3 increases in the following equilibrium reaction N23H2ˆ ˆ†‡ ˆˆ 2NH3 H ve
STATEMENT - 2
The reaction is exothermic 4. STATEMENT - 1
Reaction ‡ ˆˆˆ ˆ† 2B C K 0.28atm
Will attain equilibrium soon if the reaction is carried out in an open vessel.
STATEMENT - 2
For the atoms reaction: Kp Kc
SECTION - IV
Previous IIT- JEE Problems Objective
SECTION – VI Subjective Questions
1. For the reaction:
H2(g)I2(g)ˆ ˆ†‡ ˆˆ 2HI(g)
The equilibrium constant kp changes with
(a) total pressure (b) catalyst
(c) the amounts of H2 and I2 present (d) temperature [1981]
2. Pure ammonia is placed in a vessel at a temperature where its dissociation constant (a) is appreciable. At equilibrium
(a) kp does not change significantly with pressure
(b) does not change with pressure
(c) concentration of NH3 does not change with pressure
(d) concentration of hydrogen is less than that of nitrogen [1984]
3. At constant temperature, the equilibrium constant (kp) for the decomposition reaction
2 4 2
G 3G 2G where G is Gibbs free energy per mole of the gaseous species measured at that partial pressure.
(b) On adding N2, the equilibrium will shift to forward direction because according to IInd law of thermodynamics the entropy must increase in the direction of spontaneous reaction
(c) The catalyst will increase the rate of forward reaction by 2 times and that of backward reaction by 1.5 times
(d) None of these
SO Cl2 2(g)ˆ ˆ†‡ ˆˆ SO2(g)Cl2(g)
Is attained at 25°C in a closed container and an inert gas, helium is introduced. Which of the following statements are correct?
(a) Concentration of SO2, Cl2 and SO2Cl2 do not change
(b) More chlorine is formed
(c) Concentration of SO2 is reduced
(d) More SO2Cl2 is formed [1991]
8. For the reaction
PCl5(g) PCl3(g) Cl2(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 PCl5 at constant volume
[1991]
9. For the reaction CO(g)H O2 (g)ˆ ˆ†‡ ˆˆ CO2(g)H2(g) at a given temperature the equilibrium amount of CO2(g) can be increased by
(a) adding a suitable catalyst (b) adding an inert gas
(c) decreasing the volume of the constant (d)
Previous IIT- JEE Problems Subjective LEVEL – I
1. At a certain temperature, equilibrium constant (Kc) is 16 for the reaction SO2 (g) + NO2(g) ‡ ˆˆˆ ˆ† SO3(g) + NO(g)
If we take one mole of all the four gases in a one litre container, what would be the equilibrium concentrations of NO and NO2?
2. Show that for the reaction AB(g)‡ ˆˆˆ ˆ† A(g)B ,(g) the total pressure at which AB is 50%
dissociated is numerically equal to three times of Kp.
3. PCl5(g) at 500°K at an initial pressure of 600 mm Hg dissociates as : PCl5 PCl3 + Cl2 and the equilibrium pressure is 800 mm Hg at 500 K. Calculate KP
for the reaction assuming that no change in volume takes place.
4. Gaseous NO2 forms N2O4 according to the reaction 2NO2(g) ‡ ˆˆˆ ˆ† N2O4(g)
when 0.10 mole of NO2 is added to 1.0 L flask at 25°C, the concentration changes so that at equilibrium, [NO2] = 0.016 M and [N2O4] = 0.042M.
a) What is the value of the reaction quotient before any reaction occurs?
b) What is the value of the equilibrium constant?
5. For the following reaction,
PCl5(g) ‡ ˆˆˆ ˆ† PCl3(g) + Cl2(g)
0.4 mole of PCl5, 0.2 mole of PCl3 and 0.6 mole of Cl2 are taken in 1L flask. If Kc = 0.2 predict the direction in which reaction proceeds,
6. The equilibrium constant Kc for the reaction 2NOg) + O2(g) ‡ ˆˆˆ ˆ† 2NO2(g)
is 6.9 × 105 at 500K. A 5.0 L reaction vessel at this temperature was filled with 0.060 mole NO, 1.0 mole of O2 and 0.80 mole of NO2.
a) Is the reaction mixture at equilibrium? If not, in which direction does the reaction proceed?
b) What is the direction of the reaction if the initial amounts are 5.0 × 10–3 mole NO, 0.20 mole of O2 and 4.0 moles of NO2?
c) Can reaction quotient be zero for the case in (b)?
7. What is relation between Kp and Kc in the following equilibria?
a) CaCO3(s) ‡ ˆˆˆ ˆ† CaO(s) + CO2(g)
b) H2O(l) ‡ ˆˆˆ ˆ† H2O(g)
8. The value of Kc for the following reaction at 900°C is 0.28:
CS2(g) + 4H2(g) ˆ ˆ†‡ ˆˆ CH4(g) + 2H2S(g)
What is Kp at this temperature?
9. One mole of nitrogen is mixed with three moles of hydrogen in a 4-litre container. If 0.25% of nitrogen is converted to ammonia by the following reaction:
N2 (g) + 3H2 (g) ‡ ˆˆˆ ˆ† 2NH3 (g)
calculate the equilibrium constant Kc. What will be the value of Kc for the following equilibrium ?
1
2N2(g) + 3
2H2(g) ˆ ˆ†‡ ˆˆ NH3(g)
10. Consider the following heterogeneous equilibrium at 300 K : NH4HS (s) ˆ ˆ†‡ ˆˆ NH3(g) + H2S (g)
The total pressure of equilibrium mixture is 0.5 atm calculate Kp and Kc for the reaction.
LEVEL – II
1*. To 500 mL of 0.150 M AgNO3 solution were added 500 mL of 1.09 M Fe2+ solution and the reaction is allowed to reach on equilibrium at 25°C.
2 3
(aq) (aq) (aq) (s)
Ag Fe ˆ ˆ†‡ ˆˆ Fe Ag
For 25 mL of the solution, 30mL of 0.0832 M KMnO4 were required for oxidation.
Calculate equilibrium constant for the reaction at 25°C.
2. One mole of N2 and 3 mol of PCl5 placed in a 100 litre vessel are heated to 227 C. The 0 equilibrium pressure is 2.05 atm. Assuming ideal behaviour, calculate the degree of dissociation of PCl5 and Kp for the reaction
PCl5(g) ˆ ˆ†‡ ˆˆ PCl3 (g) + Cl2(g)
3. What is the vapour density of mixture of PCl5 at 250°C when it has dissociated to the extent of 80%.
4. For the equilibrium
2
3(s) 3(s) 3 p
LiCl 3NH ˆ ˆ†‡ ˆˆ LiCl NH 2NH (g), K 9 atm
at 40°C. A 5 litre vessel contains 0.1 mole of LiClNH3. How many mole of NH3 should be added to the flask at this temperature to derive the backward reaction for completion?
5*. Consider the reaction SO Cl (g)2 2 ‡ ˆˆˆ ˆ† SO (g) Cl (g)2 2 ; at 37 C the value of equilibrium constant for the reaction is 0.0032. It was observed that concentration of the three species is 0.050 mol/lit. each at a certain instant. Discuss what will happen in the reaction vessel?
6. In an experiment starting with 1 mole C2H5OH, 1 mole CH3COOH and 1 mole of water, the equilibrium mixture on analysis shows that 54.3% of the acid is esterified.
Calculate Kc.
7. 0.15 mol of CO taken in a 2.5 L flask is maintained at 750 K along with a catalyst so that the following reaction can take place; CO(g) + 2H (g)2 ˆ ˆ†‡ ˆˆ CH OH(g)3 . Hydrogen is introduced unitl the total pressure of the system is 8.5 atm. At equilibrium 0.08 mol of methanol is formed. Calculate:
i) Kp and Kc
ii) The final pressure if the same amount of CO and H2 as before are used but no catalyst so that the reaction does not take place.
8*. At some temperature and under a pressure of 4 atm. PCl5 is 10% dissociated. Calculate the pressure at which PCl5 will be 20% dissociated, temperature remaining same.
9. When NO and NO2 are mixed, the following equilibria are readily obtained;
2NO2 ‡ ˆˆˆ ˆ† N2O4 Kp = 6.8 atm -1 and NO + NO2 ‡ ˆˆˆ ˆ† N2O3
In an experiment when NO and NO2 are mixed in the ratio of 1: 2, the final total pressure was 5.05 atm and the partial pressure of N2O4 was 1.7 atm. Calculate:
(a) The equilibrium partial pressure of NO (b) Kp for NO + NO2 ‡ ˆˆˆ ˆ† N2O3
10*. NO and Br2 at initial pressures of 98.4 and 41.3 torr respectively were allowed to react at 300K. At equilibrium the total pressure was 110.5 torr. Calculate the value of equilibrium constant , Kp and the standard free energy change at 300K for the reaction
(g) 2(g) (g)
2NO Br ‡ ˆˆˆ ˆ† 2NOBr
LEVEL – III (Judge yourself at JEE level)
1*. For the reaction Ag(CN)2 ‡ ˆˆˆ ˆ† Ag+ + 2CN, the KC at 250 C is 4 10-19 . Calculate [Ag+ ] in solution which was originally 0.1 M in KCN and 0.03 M in AgNO3.
2. A sample of air consisting of N2 and O2 was heated to 2500K until the equilibrium N2(g)O2(g)‡ ˆˆˆ ˆ† 2NO(g)
was established with an equilibrium constant KC = 2.1 × 10–3 . At equilibrium, the moles
% of NO were 1.8. Estimate the initial composition of air in mole fraction of N2 and O2. 3*. The degree of dissociation is 0.4 at 400K and 1.0 atm for the gaseous reaction
PCl5 ‡ ˆˆˆ ˆ† PCl3 + Cl2. Assuming ideal behaviour of all the gases, calculate the density of equilibrium mixture at 400K and 1.0 atmosphere. (Atomic mass of P = 31.0 and Cl = 35.5)
4. Calculate the value of log Kp for the reaction
2 2 3
N (g) 3H (g) ˆ ˆ†‡ ˆˆ 2NH (g)
at 25°C. The standard enthalpy of formation of NH is – 46kJ and standard entropies of
5*. Solid ammonium carbamate dissociates into NH3 and CO2 as
NH4COONH2(s) ‡ ˆˆˆ ˆ† 2NH3(g) + CO2(g). The total pressure at equilibrium is 0.225atm. Calculate Kp.
6. A vessel at 1000K contains CO2 with a pressure of 0.5 atm. Some of the CO2 is converted into CO on addition of graphite. Calculate the value of K, if total pressure at equilibrium is 0.8 atm.
7. At 817°C, Kp for the reaction between CO2(g) and excess hot graphite(s) is 10 atm.
a) What are the equilibrium concentration of the gases at 817°C and a total pressure of 5 atm?
b) At what total pressure, the gas contains 5% CO2 by volume?
8. For the reaction, CO(g) + 2H2(g) ‡ ˆˆˆ ˆ† CH3OH(g); H2 is introduced into a five litre flask at 327°C, containing 0.2 mole of CO(g) and a catalyst till the pressure is 4.92 atmosphere. At this point 0.1 mole of CH3OH(g) is formed. Calculate the KC and Kp.
9*. The value of Kp is 1 × 10–3 atm–1 at 25°C for the reaction:
2NO + Cl2 ‡ ˆˆˆ ˆ† 2NOCl. A flask contains NO at 0.02 atm and at 25°C. Calculate the mole of Cl2 that must be added if 1% of the NO is to be converted to NOCl at equilibrium. The volume of the flask is such that 0.2 mole of gas produce 1 atm pressure at 25°C. (Ignore probable association of NO to N2O2).
10. When 1-pentyne (A) is treated with 4N alcoholic KOH at 175°C, it is converted slowly into an equilibrium mixture of 1.3% pentyne (A), 95.2% 2-pentyne (B) and 3.5%, of 1-2pentadiene (C). The equilibrium was maintained at 175°C. Calculate G0 for the following equilibria.:
B‡ ˆˆˆ ˆ† A : G10 ? B‡ ˆˆˆ ˆ† C : G02 ?
From the calculated value G10 andG02 indicate the order of stability of (A), (B) and (C).
18. Which of the following statements is (are) correct?
(a) An irreversible reaction goes to almost completion
(b) A reversible reaction always goes to completion if carried out in a closed vessel (c) At equilibrium, the rate of forward reaction becomes equal to that of backward
reaction
(d) In the beginning, the rate of backward reaction is much greater than that of forward reaction.
19. The value of equilibrium constant of a reversible reaction at a given temperature (a) depends on the initial concentration of reactants
(b) depends on the concentration of products at equilibrium
(c) gets reversed when the mode of representation of the reaction is reversed
(d) changes when the unit of active mass is changed 20. Which of the following statements is (are) correct?
(a) The value of equilibrium constant for a particular reaction is constant under all conditions of temperature and pressure
(b) The units of Kc for the reaction H O2 ‡ ˆˆˆ ˆ† H O2 (g) are mol L–1 (c) In the reaction
CaCO3(s)ˆ ˆ†‡ ˆˆ CaO(s)CO2(g), [CaCO ] [CaO] 13 (d) Kp is always greater than Kc for a particular reaction
21. In the dissociation of 2HI‡ ˆˆˆ ˆ† H2I2, the degree of dissociation will be affected by the (a) addition of inert gas (b) addition of H2 and I2
(c) increase of temperature (d) increase of pressure 22. In which of the following gaseous equilibria, Kp is less than Kc? (a) N O2 4‡ ˆˆˆ ˆ† 2NO2 (b) 2HI‡ ˆˆˆ ˆ† H2I2 (c) 2SO2O2‡ ˆˆˆ ˆ† 2SO3 (d) N23H2‡ ˆˆˆ ˆ† 2NH3 23. Which of the following equilibria is (are) not affected by pressure?
(a) 2SO2(g) O2(g)‡ ˆˆˆ ˆ† 2SO3(g) (b) H2(g)I2(g)ˆ ˆ†‡ ˆˆ 2HI(g)
(c) 2NO(g)O2(g)‡ ˆˆˆ ˆ† 2NO2(g) (d) N2(g)O2(g)‡ ˆˆˆ ˆ† 2NO(g)
24. Which of the following will favour the formation of products in the following reaction?
A(g)2B(g) 3C (g) D(g) heat
(c) Addition of B (d) Removal of C 25. The equilibrium concentration of C2H4 in the gas phase reaction C H2 4H2‡ ˆˆˆ ˆ† C H2 6 H 32.7kcal, can be increased by (a) removal of C2H6 (b) removal of H2
(c) decreasing temperature (d) increasing pressure
SECTION – III
Comprehension Type Questions
Write-up IA chemical reaction in the laboratory is carried out under the condition of constant temperature and pressure. The condition of spontaneity in terms of enthalpy and entropy are, respectively, H 0 and S 0 whereas condition of equilibrium are, respectively,
H = 0 and S = 0. An endothermic reaction is driven by increase in entropy i.e. increase in disorderness. The two criteria combined together, the condition of reversibility and irreversibility are as follows:
GP, T = H – TS 0, where equal to sign refers to reversibility and less than sign refers to irreversibility. Reversibility is the condition of equilibrium whereas irreversibility is the condition of spontaneity. A reversible reaction is characterised by equilibrium constant (K), the magnitude of which measures the position of equilibrium i.e. how far a chemical reaction will go to completion before attainment of equilibrium. The position of equilibrium constant of a reaction with temperature is given by Van’t Hoff equation of thermodynamics which is as follows:
2
d ln K H
dT RT
This equation can be integrated assuming H to be independent of temperature. Within the short interval of temperature.
For a gaseous equilibria k can be expressed Kc and Kp related as
ng
p c
K K (RT)
Where the symbols have their usual meanings. ng of a reaction can be found out from the unit of equilibrium, though it is not customary to write unit of equilibrium constant.
Another way of finding ng of a reaction is to use the equation
H = E + ng RT Where the terms have their usual meanings.
Knowing K and reaction quotient it is possible to calculate free energy change of a reaction using the equation:
G = G0 + RTlnQ
At equilibrium Q = K and G = 0
So, G0 = –RTlnK where G0 is the free energy change of the reaction in the standard state.
The standard state of a substance is defined as the state of unit activity at 25°C. In the case of solution of a substance the activity is taken to be molar concentration while for a gas it is pressure in atm.
The standard free energy of an element is taken to be zero.
1. At 27°C the heat of reaction at constant pressure is 600 cals more than that at constant volume. The ratio of Kp to Kc of the reaction is:
(a) 24.63 (b) (24.63)2 (c) 0.6 (d) 0.36 2. For the reaction:
NH HS4 (s)ˆ ˆ†‡ ˆˆ NH3(g) H S2 (g) Kp and Kc are interrelated as
(a) Kp = KcRT (b) Kp = Kc 2 (RT) (c) Kp = Kc(RT)2 (d) Kp = Kc/RT
3. The Kp of a reaction is 10 atm–2 at a temperature T on Kelvin scale. Hence (a) Kp = Kc (b) Kp Kc
(c) Kp Kc (d) Can’t be predicted 4. The Kc of a reaction is 4.0 mol2 L–2 at 27°C. Hence Kp of the reaction is:
(a) 4 (0.0821 × 300)2 atm2 (b) 4 (2 × 300)2 atm2
(c) 2 2 chemical equilibria must be maintained to ensure physiological well being. Transport of oxygen by blood depends on the reversible combination of oxygen with haemoglobin. In blood, haemoglobin, oxygen and oxyhaemoglobin are in equilibrium.
the thermodynamic equilibrium constant of the reaction. Both are related to each other at temperature T by the following relation:
G° = –2.303 RT log KC
and G° = –2.303 RT log KP (incase of ideal gas)
This equation represents one of the most important results of thermodynamics and relates to the equilibrium constant of a reaction to a thermodynamic property.
It is sometimes easier to calculate the free energy in a reaction rather than to measure the equilibrium constant.
Standard free energy change can be thermodynamically calculated as G° = H° –TS°
Here H° = standard enthalpy change S° = standard entropy change.
9. Which of the following statement is correct for a reversible process in state of equilibrium
(a) G = –2.303 RT log K (b) G = 2.303 RT log K (c) G° = –2.303 RT log K (d) G° = 2.303 RT log K 10. At 490°C, the value of equilibrium constant; KP is 45.9 the reaction H2(g) + I2(g) ˆ ˆ†‡ ˆˆ 2HI(g)
Calculate the value of G° for the reaction at that temperature (a) –3.5 kcal (b) 3.5 kcal (c) 5.79 kcal (d) –5.79 kcal
11. Calculate the equilibrium concentration ratio of C to A if 2.0 mol each of A and B were allowed to come to equilibrium at 300 K
A + B ‡ ˆˆˆ ˆ† C + D G° = 460 Cal (a) 1.0 (b) 0.5
(c) 0.8 (d) 0.679
Write-up IV
The equilibrium constants (Kp and Kc) of a gaseous equilibria say aA(g) bB(g)‡ ˆˆˆ ˆ† cC(g) dD(g)
are interrelated as : Kp K (RT)c ng
where ng = (c + d) – (a + b
The heat of reactions : H and E are interrelated according to the equation:
H = E + ngRT.
12. H of a reaction is 600 cals more than E at 27°C. What is the ratio of Kp and Kc of a reaction at 27°C? (R = 1.987 2 cals K–1 mol–1 ) = 0.0821 L atm K–1 mol–1 .
(a) 1.2 (b) 24.63 (c) 49.26 (d) 2.4
13. Solid A was heated in a sealed vessel when pressure developed 65.68 atm at 127°C due to the attainment of following equilibrium
A(s)‡ ˆˆˆ ˆ† B(g) C(g)
Hence Kc of the reaction at 127°C is:
(a) 1
32.84 (b) 1.0 (c) 2
32.84 (d) can’t be calculated
Write-up VAmmonia is manufactured by the Haber process represented by the equilibrium:
N2(g) 3H2(g)‡ ˆˆˆ ˆ† 2NH3(g) H0 = –184.4 kJ
The optimum conditions for the production of ammonia are a pressure of about 200 atm and a temperature of around 700K. Iron oxide containing small amounts of K2O and Al2O3 is used as catalyst so as to increase the rate of attainment of equilibrium. Annual world production of ammonia now exceeds 10 million tonnes.
14. According to Le-Chateliers principle the favourable condition for good yield of NH3
(a) Low pressure and low temperature (b) High pressure and low temperature (c) Low pressure and high temperature (d) High pressure and high temperature
15. In absence of catalyst during Haber’s process of ammonia synthesis (a) yield of NH3 will decrease
(b) yield of NH3 will remain the same
(c) equilibrium position will get shifted in the backward direction (d) equilibrium will never set up
SECTION – IV Subjective Questions
LEVEL – I
1. Kc for equilibrium A(g)‡ ˆˆˆ ˆ† B(g)C(g) is 0.45 at 200°C. One litre of a container holds 0.2 mole of A, 0.3 mole of B and 0.3 mole of C at equilibrium. Calculate the new equilibrium concentrations of A, B and C if the volume of container at same temperature is: a) Halved; (b) Doubled
2. Show that for the reaction AB(g)‡ ˆˆˆ ˆ† A(g)B ,(g) the total pressure at which AB is 50%
dissociated is numerically equal to three times of Kp.
3. PCl5(g) at 500°K at an initial pressure of 600 mm Hg dissociates as : PCl5 PCl3 + Cl2 and the equilibrium pressure is 800 mm Hg at 500 K. Calculate KP
for the reaction assuming that no change in volume takes place.
4. Gaseous NO2 forms N2O4 according to the reaction 2NO2(g) ˆ ˆ†‡ ˆˆ N2O4(g)
when 0.10 mole of NO2 is added to 1.0 L flask at 25°C, the concentration changes so that