Chemical Equilibrium MCQs with Answers
At equilibrium, the concentration of reactants and products is:
Maximum
Minimum
Unstable
Constant
Which statement correctly describes a reversible reaction?
Only the forward reaction occurs; the reverse reaction does not take place.
Both forward and reverse reactions occur, but under different conditions.
Forward and reverse reactions take place at different times and under different conditions.
Forward and reverse reactions occur simultaneously under the same conditions.
For the reaction: 4NH3+5O2⇌4NO+6H2O
The units of the equilibrium constant (Kc) are:
Concentration² (Conc.²)
Concentration⁻¹ (Conc.⁻¹)
No units
Concentration (Conc.)
One mole of HI was sealed in a tube and heated at 440°C until equilibrium was reached. If HI was found to be 50% dissociated, the equilibrium constant Kc for the reaction is:
For what value of Kc is the forward reaction almost complete?
One mole of ethyl alcohol was treated with one mole of acetic acid at 25°C. If 2/3 of the acid changes into ester at equilibrium, the equilibrium constant of the reaction will be:
At equilibrium, the concentrations of SO₂, O₂, and SO₃ are 2M, 2M, and 4M, respectively, for the reaction:
2SO2+O2⇌2SO3
What is the Kc value?
For the reaction:
CO+2H2⇌CH3OH, ΔH=−92kJ/mol
At equilibrium, the concentrations of CO, H₂, and CH₃OH become constant. What will happen?
Reaction speeds up.
Reaction slows down.
Equilibrium state is disturbed.
Equilibrium state remains undisturbed.
If Kc value is very small, the equilibrium position will shift:
Toward products (right).
It remains unchanged.
It is always a constant value.
Toward reactants (left).
If Kc value is very large, the equilibrium position will shift:
Toward reactants (left).
It remains unchanged.
It is always a constant value.
Toward products (right).
For the reaction: H2+I2⇌2HI
The equilibrium constant (K) is affected by:
Total pressure
Catalyst
Concentration
Temperature
Which of the following correctly represents the relationship between Kp and Kc?
Kp = Kc (R)Δⁿ
Kp = Kc (RT)Δⁿ
Kp = Kc (R/N)Δⁿ
Kc = Kp (RT)Δⁿ
For the given reaction: PCl5⇌PCl3+Cl2
For the reaction H2+I2⇌2HI
If the equilibrium concentrations of H₂, I₂, and HI are 8, 3, and 24mol/dm³, respectively, what is the equilibrium constant Kc?
For the following reaction in the gaseous phase:
CO +1/2O2 ⇌ CO2, Kc/Kp is
(RT)^−(1/2)
(RT)^ (1/2)
(RT) ^−1
(RT) ^1
In the reaction:
A2(g)+4B(g)⇌2AB4(g)
If ΔH is negative, the formation of AB(g) will be favored at:
Low temperature and low pressure
High temperature and low pressure
High temperature and high pressure
Low temperature and high pressure
For the reaction:
N2+3H2⇌2NH3+Heat ,ΔH=−41.02kJ/mol
The forward reaction is favored by:
Adding NH₃ at equilibrium
Adding a catalyst
Decreasing the concentration of H₂
Decreasing temperature
In a given system, water and ice are in equilibrium. If pressure is applied, what will happen?
More ice is formed
The amount of ice and water remains the same
Both A and B
More ice is melted
If temperature is increased, how will the reaction shift?
N2+3H2⇌2NH3+Heat ,ΔH=−ve/mol
Forward direction
Remains unchanged
Decreases the rate of reaction
Backward direction
In the Haber process, equilibrium gas mixture contains ___ NH₃ by volume.
The catalyst used in the Haber process is:
Which of the following is a basic buffer solution?
HF / NaF
H₂CO₃ / Na₂CO₃
(COOH)₂ / (COONa)₂
NH₄OH / NH₄Cl
Buffer action can be explained by:
Common ion effect
Le Chatelier’s principle
Mass action law
All of these
A basic buffer solution can be prepared by mixing:
A strong acid and its salt with a weak base
A strong base and its salt with a weak acid
A weak acid and its salt with a strong base
A weak base and its salt with a strong acid
The pH of an ideal buffer solution is:
A buffer solution contains equal concentrations of acid (X) and its conjugate base, where the Ka for X is 10⁻³. The pH of the buffer is:
Which Henderson equation is correct?
pH = pKa + log ([Acid] / [Salt])
pOH = pKb + log ([Salt] / [Base])
pH = pKb + log ([Base] / [Acid])
pH=pKa+log([salt]/[acid])
For an acidic buffer, pH>pKa if:
[Salt] = [Acid]
[Salt] < [Acid]
[Salt] > [Base]
[Salt] > [Acid]
When CO₂ gas is passed through a saturated solution of calcium carbonate (CaCO₃), the solubility of CaCO₃:
Increases
First increases, then decreases
Remains unchanged
Decreases
If the ionic product = Ksp, the solution is
Supersaturated
Saturated
Dilute
Unsaturated
The ionization of BaSO₄ is suppressed by:
Increasing temperature
Adding NaCl
Decreasing temperature
Adding BaCl₂
If ionic product > Ksp, then the solution is:
Unsaturated
Ideal
Saturated
Supersaturated
The solubility product (Ksp) is applicable only for substances whose molar concentrations are:
Equal to 0.1M
Equal to1M
Greater than 0.1
Equal to or less than 0.01
In a saturated solution of AB, the molar concentration of A⁺ and B⁻ ions is 1 × 10⁻⁵ M. Find Ksp?
1.0 × 10⁻⁵
2.0 × 10⁻²
1.5 × 10⁻⁵
1.0 × 10⁻¹⁰
For a sparingly soluble salt AB3, the solubility is "S" mol/dm³. The solubility product (Ksp) is given by:
Ksp = S²
Ksp = 4S³
Ksp = 27S³
Ksp = 27S⁴
Units of equilibrium constant (Kc) for the following reaction:
A+B⇌2C
mol/dm³
mol⁻¹ dm³
mol² dm⁻⁶
No unit
If Na₂SO₄ is added to a solution of BaSO₄, BaSO₄ will precipitate due to:
Decrease in temperature
Increase in solubility
Salt hydrolysis
Common ion effect
If the temperature is decreased, what will happen to the formation of NH₃, given that the reaction is reversible and exothermic?
The formation of NH₃ will decrease
The reaction will remain unaffected
NH₃ will start decomposing
The formation of NH₃ will increase
A buffer solution is a solution that resists the change in:
A chemical substance that releases H⁺ ions when dissolved in water is known as:
Neutral
Base
Amphoteric
Acid
The pH of human blood is:
The equilibrium constant (Kc) for the reaction N₂(g) + O₂(g) ⇌ 2NO(g) is 4.0 x 10⁻⁴ at a certain temperature. What is the value of Kc for the reaction 2NO(g) ⇌ N₂(g) + O₂(g) at the same temperature?
4.0 x 10⁻⁴
2.0 x 10⁻²
2.5 x 10⁴
2.5 x 10³
What will be the pH of an HCl solution with a concentration of 10⁻² M?
For maximum yield of NO₂, according to Le Chatelier’s Principle, the reaction:
Δ2NO + O₂ ⇌ 2NO₂ ΔH=−114 kJ/mol
should be carried out at:
High temperature and high pressure
High temperature and low pressure
Low temperature and low pressure
Low temperature and high pressure
What is the relationship between pH and pKa?
pH=pKa−log[Acid/Base]
pKa=pH−log[Acid/Base]
pH=pKa+log[ Acid /Base]
pH=pKa+log[Base/Acid]
Which of the following is the correct representation for Ksp of BaSO₄?
BaSO₄ ⇌Ba²⁺ + SO₄²⁻
Ksp = [BaSO₄] / ([Ba²⁺][SO₄²⁻])
Ksp = [Ba²⁺][SO₄²⁻] / [BaSO₄]
Ksp = [Ba²⁺] + [SO₄²⁻]
Ksp = [Ba²⁺][SO₄²⁻]
6.50 - 7.00
7.20 - 7.25
7.50 - 8.00
7.35 - 7.40
At 25°C, the solubility product constant (Ksp) for the PbSO₄ system is:
1.0 × 10⁻¹⁴ mol² dm⁻⁶
1.8 × 10⁻¹⁰ mol² dm⁻⁶
6.4 × 10⁻⁷ mol² dm⁻⁶
1.6 × 10⁻⁸ mol² dm⁻⁶
For which of the following equilibrium reactions, K has no units?
A+3A ⇌2C
A+2B ⇌2C
2A+B ⇌2C
A+B ⇌C+D
Consider the following reversible reaction:
CH3CH2OH + CH3COOH ⇌ CH3COOCH2CH3 + H2O
The initial concentrations are:
Ethanol (CH₃CH₂OH) = 1 mol
Acetic acid (CH₃COOH) = 1 mol
Ethyl acetate (CH₃COOCH₂CH₃) = 0 mol
Water (H₂O) = 0 mol
At equilibrium, the concentrations are:
CH₃CH₂OH = 0.333 mol
CH₃COOH = 0.333 mol
CH₃COOCH₂CH₃ = 0.666 mol
H₂O = 0.666 mol
If 1 mole each of CH₃CH₂OH and CH₃COOH are added, what will be the new equilibrium concentrations?
[CH₃COOH] = 0.333, [CH₃COOCH₂CH₃] = 1.666, [CH₃CH₂OH] = 1.333, [H₂O] = 0.666
[CH₃COOH] = 1.333, [CH₃COOCH₂CH₃] = 0.666, [CH₃CH₂OH] = 0.333, [H₂O] = 1.666
[CH₃COOH] = 0.333, [CH₃COOCH₂CH₃] = 1.333, [CH₃CH₂OH] = 0.333, [H₂O] = 1.333
[CH₃COOH] = 0.666, [CH₃COOCH₂CH₃] = 1.333, [CH₃CH₂OH] = 0.666, [H₂O] = 1.333
BaF₂ is sparingly soluble, having a solubility product (Ksp) of 1.5 × 10⁻⁶. What will be its solubility?
5.2 × 10⁻³ M
8.1 × 10⁻³ M
1.1 × 10⁻³ M
7.2 × 10⁻³ M
The product of ion concentrations in a saturated solution of a sparingly soluble salt at 310 K, each raised to the power of its stoichiometric coefficient, is known as
Ionic product
Equilibrium constant (Kc)
Reaction quotient (Q)
Solubility product (Ksp)
Which of the following factors influence a reversible chemical reaction based on Le Chatelier’s Principle?
catalyst
Volume and catalyst
None of these
Temperature, pressure, and concentration
Which of the following factors affect the equilibrium position?
Catalyst only
Only concentration
None of these
Temperature, concentration, and pressure
The Kc unit for the reaction:
A+3B⇌2C
mol dm⁻³
mol² dm⁻⁶
mol⁻³ dm⁹
mol⁻² dm⁶
Which one of the following bases has the highest Kb value?
What is the pH of 0.01 M HCl?
If the pKa of formic acid (HCOOH) is 3.75, the pH of an equimolar solution of formic acid and sodium formate is:
Precipitation takes place when the ionic product of the ions in a solution is:
Less than Ksp
Equal to Ksp
Equal to unity
Greater than Ksp
In the equation Kp = Kc (RT)ⁿ, if Δn > 0, then:
The pKa values of some acids at room temperature are given below. Which one is the strongest acid?
HNO₃ (pKa = -1.4)
HCl (pKa = -7)
H₂SO₄ (pKa = -3)
HI (pKa = -10)
N2 + 3H2 ⇌ 2NH3 + Heat
The production of NH₃ will be highest at:
High temperature and low pressure
High temperature and high pressure
Low temperature and low pressure
Low temperature and high pressure
Explanation:Since the forward reaction is exothermic, a lower temperature favors NH₃ formation. Additionally, since fewer gas molecules are on the right side, increasing pressure shifts equilibrium toward NH₃ production.
Ice and water are in equilibrium within a closed system. If the pressure is decreased, the equilibrium will shift:
Forward, causing more ice to melt.
Affecting the entire system at equilibrium.
No change in equilibrium.
Reverse, leading to more water freezing.
A+B ⇌ C + Heat
As the forward reaction is exothermic, an increase in temperature shifts the equilibrium:
To the right, increasing C
To the right, increasing A and B while C remains the same
To the left, decreasing A and B while increasing C
To the left, increasing A and B, while decreasing C
Which statement is correct regarding the reaction:
2NOCl ⇌ 2NO + Cl₂
Kp < Kc
Kp = Kc
None of the above
Kp > Kc
Which industrial process is represented by the reaction: N₂ + 3H₂ ⇌ 2NH₃?
Contact process
Solvay process
Avogadro’s law
Haber’s process
In a gaseous reaction where the number of moles of reactants and products are the same, the relationship between Kp and Kc is:
None of these
Kc < Kp
Kc > Kp
Kp = Kc
The purification of table salt (NaCl) by passing HCl gas through its saturated aqueous solution is an example of:
Law of mass action
Hess’s law
Henry’s law
Common ion effect
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