NEET Chemistry Chemical Equilibrium Revision Notes

Question. Which of the following conditions represents an equilibrium?
a. Freezing of ice in a open vessel, temperature of ice is constant
b. Few drops of water is present along with air in a balloon, temperature of balloon is constant
c. Water is boiling in an open vessel over stove, temperature of water is constant
d. All the statements (a), (b) and (c) are correct for the equilibrium
Answer : B

Question. The reaction CaCO₃ CaO + CO₂ (g) ⇌ goes to completion in lime kiln because:
a. of the high temperature
b. CaO is more stable than CaCO₂
c. CaO is not dissociated
d. CO₂ escapes continuously
Answer : D

Question. A reversible reaction is one which?
a. Proceeds in one direction
b. Proceeds in both directions
c. Proceeds spontaneously
d. All the statements are wrong
Answer : B

Question. Which of the following is a characteristic of a reversible reaction?
a. Number of moles of reactants and products are equal
b. It can be influenced by a catalyst
c. It can never proceed to completion
d. None of the above
Answer : C

Question. The decomposition of N₂ O₄ to NO₂ is carried out at 280K in chloroform. When equilibrium has been established, 0.2 mol of N₂ O₄ and 2 x 10⁻³ mol of NO₂ are present in 2 litre solution. The equilibrium constant for reaction N₂ O₄ ⇌ 2NO₂ is:
a. 1 x 10⁻²
b. 2 x 10⁻²
c. 1 x 10⁻⁵
d. 2 x 10⁻⁵
Answer : C

Question. A reaction is A + B→ C + D. Initially we start with equal concentration of A and B. At equilibrium we find  the moles of C are two times of A. What is the equilibrium constant of the reaction?
a. 4
b. 2
c. 1 / 4
d. 1 / 2
Answer : A

Question. The rate constant for forward and backward reactions of hydrolysis of ester are 1.1 10⁻² and 1.5 x 10⁻³ per minute respectively. Equilibrium constant for the reaction is CH₃ COOC₂ H₅ + H₂ O ⇌ CH₃ COOH + C₂ H₅ OH
a. 4.33
b. 5.33
c. 6.33
d. 7.33
Answer : D

Question. 2 moles of PCl₅ were heated in a closed vessel of 2 litre capacity. At equilibrium, 40% of PCl₅ is dissociated into PCl₃ and Cl₃. The value of equilibrium constant is:
a. 0.266
b. 0.53
c. 2.66
d. 5.3
Answer : A

Question. Unit of equilibrium constant for the reversible reaction H₂ + I₂ ⇌ 2HI is:
a. mol^–1 litre
b. mol^–2 litre
c. 1 mol litre−
d. None of these
Answer : D

Question. For the chemical equilibrium, CaCO₃ (s) ⇌ CaO(s) + CO₂ (g), ΔH_r° can be determined from which one of the following plots:

Answer : A

Question. In which of the following equilibria, the value of K_p is less than K_c ?
a. H₂ + I₂ ⇌ 2HI
b. N₂ + 3H₂ ⇌ 2NH₃
c. N₂ + O₂ ⇌ 2NO
d. CO + H₂ O ⇌ CO₂ + H₂
Answer : B

Question. 4.5 moles each of hydrogen and iodine heated in a sealed ten litre vessel. At equilibrium, 3 moles of HI were found. The equilibrium constant for H₂ (g) + I₂ (g) ⇌ 2HI(g) is?
a. 1
b. 10
c. 5
d. 0.33
Answer : A

Question. An equilibrium mixture of the reaction 22H₂ S(g) ⇌ 2H₂ (g) +S₂ (g) had 0.5mole H₂ S ,0.10 mole H₂ and 0.4 mole S₂ in one litre vessel. The value of equilibrium constant (K) in mole litre-1 is:
a. 0.004
b. 0.008
c. 0.016
d. 0.160
Answer : C

Question. At 3000 K the equilibrium pressures of CO₂, CO and O₂ are 0.6,0.4 and 0.2 atmospheres respectively. p K for the reaction, 2CO₂ ⇌ 2CO + O₂ is:
a. 0.089
b. 0.0533
c. 0.133
d. 0.177
Answer : A

Question. The equilibrium SO₂CI_2(g) ⇌ SO_2(g) + Cl_2(g) is attained at 25°C in a closed container and an inert gas helium is introduced which of the following statement is correct?
a. More chlorine is formed
b. Concentration of SO₂ is reduced
c. More SO₂ Cl₂ is formed
d. Concentration of SO₂ Cl₂ ,SO₂ and Cl₂ does not change
Answer : D

Question. Sodium sulphate dissolves in water with evolution of heat. Consider a saturated solution of sodium sulphate. If the temperature is raised, then according to Le-Chatelier principle:
a. More solid will dissolve
b. Some solid will precipitate out from the solution
c. The solution will become supersaturated
d. Solution concentration will remain unchanged
Answer : B

Question. Consider the equilibrium: N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g) ; ΔH = – 93.6 KJ.
The maximum yield of ammonia is obtained by:
a. Decrease of temp. and increase of pressure
b. Increase of temp. and decrease of pressure
c. Decrease of both the temp. and pressure
d. Increase of both the temp. and pressure
Answer : A

Question. Amongst the following chemical reactions the irreversible reaction is:
a. H₂ + I₂ ⇌ HI
b. AgNO₃ + NaCl ⇌ AgCl + NaNO₂
c. CaCO₃ ⇌ CaO + CO₂
d. O₂ + 2SO₂ ⇌ 2SO₂
Answer : B

Question. In chemical reaction A ⇌  B, the system will be known in equilibrium when?
a. A completely changes to B
b. 50% of A changes to B
c. The rate of change of A to B and B to A on both the sides are same
d. Only 10% of A changes to B Irreversible and Reversible Reactions
Answer : C

Question. For the reaction H₂ (g) + I₂ (g) ⇌ 2HI(g), the equilibrium constant changes with:
a. Total pressure
b. Catalyst
c. The amounts of H₂ and I₂ taken
d. Temperature
Answer : D

Question. Calculate ΔG° for conversion of oxygen to ozone 3/ 2 O₂ (g)→ O₃ (g) at 298 K, if K_p for this conversion is 2.47 x 10⁻²⁹ 
a. 163 kJ mol⁻¹
b. 2.4 x 10² kJ mol⁻¹
c. 1.63 kJ mol⁻¹
d. 2.38 x 10⁶ kJ mol⁻¹
Answer : A

Question. When the pressure is applied over system ice ⇌ water what will happen?
a. More water will form
b. More ice will form
c. There will be no effect over equilibrium
d. Water will decompose in H2 and O2
Answer : A

Question. The reactionA + B ⇌ C+ D+ heat has reached equilibrium.
The reaction may be made to proceed forward by:
a. Adding more C
b. Adding more D
c. Decreasing the temperature
d. Increasing the temperature
Answer : C

Question. Following gaseous reaction is undergoing in a vessel C₂ H₄ + H₂ ⇌ C₂ H₆ ;ΔH = −32.7 Kcal Which will increase the equilibrium concentration of C₂ H₆ :
a. Increase of temperature
b. By reducing temperature
c. By removing some hydrogen
d. By adding some C₂ H₆
Answer : B

Question. N₂ + O₂ ⇌ 2NO − Qcals In the above reaction which is the essential condition for the higher production of NO
a. High temperature
b. High pressure
c. Low temperature
d. Low pressure
Answer : A

Question. Which of the following reactions proceed at low pressure?
a. N₂ + 3H₂ ⇌ 2NH₃
b. H₂ + I₂ ⇌ 2HI
c. PCl₅ ⇌ PCl₃ + Cl₂
d. N₂ + O₂ ⇌ 2NO
Answer : C

Question. In the following reversible reaction 2SO₂ + O₂ ⇌ 2SO₃ + QCal Most suitable condition for the higher production of SO₃ is:
a. High temperature and high pressure
b. High temperature and low pressure
c. Low temperature and high pressure
d. Low temperature and low pressure
Answer : C

Question. The effect of increasing the pressure on the equilibrium 2A + 3B⇌ 3A + 2B is:
a. Forward reaction is favoured
b. Backward reaction is favoured
c. No effect
d. None of the above
Answer : C

Question. For the equilibrium 2NO₂ (g) ⇌ N₂ O₄ (g) + 14.6k cal the increase in temperature would:
a. Favour the formation of N₂ O₄
b. Favour the decomposition of N₂ O₄
c. Not alter the equilibrium
d. Stop the reaction 
Answer : B

Question. On the velocity in a reversible reaction, the correct explanation of the effect of catalyst is:
a. It provides a new reaction path of low activation energy
b. It increases the kinetic energy of reacting molecules
c. It displaces the equilibrium state on right side
d. It decreases the velocity of backward reaction
Answer : A

Question. According to Le-chatelier principle, if heat is given to solid-liquid system, then:
a. Quantity of solid will reduce
b. Quantity of liquid will reduce
c. Increase in temperature
d. Decrease in temperature
Answer : A

Question. In the reactionA(g) + 2B(g) ⇌ C(g) +QkJ, greater product will be obtained or the forward reaction is favoured by:
a. At high temperature and high pressure
b. At high temperature and low pressure
c. At low temperature and high pressure
d. At low temperature and low pressure
Answer : C

Question. Consider the reaction HCN_(aq) H⁺_(aq) CN⁻_(aq) At equilibrium, the addition of (aq) CN⁻_(aq) would:
a. Reduce HCN_(aq) concentration
b. Decrease the H+_(aq) ion concentration
c. Increase the equilibrium constant
d. Decrease the equilibrium constant
Answer : B

Question. In the gaseous equilibrium H₂ X₂ + heat ⇌ 2HX, the formation of HX will be favoured by:
a. High pressure and low temperature
b. High temperature and low pressure
c. Low temperature and low pressure
d. High temperature and high pressure
Answer : B

Question. In which of the following gaseous equilibrium an increase in pressure will increase the yield of the products?
a. 2HI ⇌ H₂ + I₂
b. 2SO₂ + O₂ ⇌ 2SO₃
c. H₂ + Br₂ ⇌ 2HBr
d. H₂ O + CO ⇌ H₂ + CO₂
Answer : B

Question. Which of the following factors will favour the reverse reaction in a chemical equilibrium?
a. Increase in the concentration of one of the reactants
b. Removal of at least one of the product at regular time intervals
c. Increase in the concentration of one or more products 
d. None of these
Answer : C

Question. In the formation of SO₃ by contact process, the conditions used are:
a. Catalyst, optimum temperature and higher conce ntration of reactants
b. Catalyst, optimum temperature and lower concentration of reactants
c. Catalyst, high temperature and higher concentration of reactants
d. Catalyst, low temperature and lower concentration of reactants
Answer : A

Question. Given reaction is 2X_(gas) + Y_(gas) ⇌ 2Z_(gas) + 80 kcal which combination of pressure and temperature gives the highest yield of Z at equilibrium?
a. 1000 atm and 500 °C
b. 500 atm and 500 °C
c. 1000 atm and 100 °C
d. 500 atm and 100 °C
Answer : C

Question. The formation of NO₂ in the reaction 2NO + O₂ ⇌ 2NO₂ + heat is favoured by:
a. Low pressure
b. High pressure
c. Low temperature
d. Reduction in the mass of
Answer : B, C

Question. The exothermic formation of ClF₃ is represented by the equation Cl_2(g) + 3F_2(g) ⇌ 2ClF_3(g) ; ΔH = −329 kJ Which of the following will increase the quantity of ClF₃
in an equilibrium mixture of Cl₂ ,F₂ and ClF₃ ?
a. Increasing the temperature
b. Removing Cl₂
c. Increasing the volume of the container
d. Adding F₂
Answer : D

Question. Raising the temperature of an equilibrium system:
a. Favours the exothermic reaction only
b. Favours the endothermic reaction only
c. Favours both the exothermic and endothermic reactions
d. Favours neither the exothermic nor endothermic reactions
Answer : B

Question. The endothermic reaction (M+ N ⇆ P) is allowed to attain equilibrium at 25°. Formation of P can be increased by:
a. Raising temperature
b. Lowering temperature
c. Keeping temperature constant
d. Decreasing the concentration of M and N
Answer : A

Question. According to Le-chatelier's principle, an increase in the temperature of the following reaction will: N₂ + O₂ ⇌ 2NO − 43, 200kcal
a. Increase the yield of NO
b. Decrease the yield of NO
c. Not effect the yield of NO
d. Not help the reaction to proceed in forward direction
Answer : A

Question. In the manufacture of NH₃ by Haber's process, the condition which would give maximum yield is: N₂ + 3H₂ ⇌ 2NH₃ +Qkcal
a. High temperature, high pressure and high concentrations of the reactants
b. High temperature, low pressure and low concentrations of the reactants
c. Low temperature and high pressure
d. Low temperature, low pressure and low concentration of H₂
Answer : C

Question. Suppose the reaction PCl_5(s) ⇌ PCl_3(s) + Cl_2(g) is in a closed vessel at equilibrium stage. What is the effect on equilibrium concentration of Cl_2(g) by adding PCl₅ at constant temperature?
a. Decreases
b. Increases
c. Unaffected
d. Cannot be described without the value of Kp
Answer : B

Question. In which of the following equilibrium reactions, the equilibrium would shift to the right, if total pressure is increased?
a. N₂ + 3H₂ ⇌ 2NH₃
b. H₂ + I₂ ⇌ 2HI
c. H₂ + Cl₂ ⇌ 2HCl
d. N₂ O₄ ⇌ 2NO
Answer : A

Question. Formation of SO₃ takes place according to the reaction 2SO₂ + O₂ ⇌ 2SO ;ΔH = −45.2 kcal
Which of the following factors favours the formation of SO₃ ?
a. Increase in temperature
b. Increase in pressure
c. Removal of oxygen
d. Increase in volume
Answer : B