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All questions of Equilibrium for NEET Exam

Ca(HCO3)2 is strongly heated and after equilibrium is attained, temperature changed to 25° C.

Kp = 36 (pressure taken in atm)
Thus, pressure set up due to CO2 is
  • a)
    36 atm
  • b)
    18 atm
  • c)
    12 atm
  • d)
    6 atm
Correct answer is 'D'. Can you explain this answer?

Mira Joshi answered
The reaction is as follow:-
Ca(HCO3)2(s)⇌CaO(s) + 2CO2 (g) + H2O(g)
At 25° C H2O goes in liquid state
Kp = (PCaO)1×(PCO2)2
(PCa(HCO3)2)
Since, Ca(HCO3)2, CaO and H2O are not in gaseous state, so their partial pressure is taken 1.
Putting all values, we have
36 = (PCO2)2 
Or PCO2 = 6 atm

Which of the following is more acidic? A solution with pH 5 or a solution with pH 3
  • a)
    solution with pH 5
  • b)
    solution with pH 3
  • c)
    both are equally acidic
  • d)
    cannot be predicted from pH values
Correct answer is option 'B'. Can you explain this answer?

Dipika Singh answered
**Solution:**

**pH Scale:**
The pH scale is used to measure the acidity or alkalinity of a solution. It ranges from 0 to 14, with 7 being considered neutral. Solutions with pH values below 7 are considered acidic, while solutions with pH values above 7 are considered alkaline or basic.

**Explanation:**
In this case, we are comparing a solution with pH 5 to a solution with pH 3 to determine which one is more acidic.

**pH 5 Solution:**
A solution with pH 5 is acidic because it is below the neutral pH of 7. However, it is less acidic compared to a solution with pH 3.

**pH 3 Solution:**
A solution with pH 3 is also acidic because it is below the neutral pH of 7. However, it is more acidic compared to a solution with pH 5.

**Comparing pH Values:**
The pH scale is logarithmic, which means that each whole number change in pH represents a tenfold change in acidity. In other words, a solution with pH 3 is ten times more acidic than a solution with pH 4, and a hundred times more acidic than a solution with pH 5.

Therefore, we can conclude that a solution with pH 3 is more acidic compared to a solution with pH 5.

**Conclusion:**
In summary, a solution with pH 3 is more acidic compared to a solution with pH 5. The pH scale is logarithmic, and each whole number change represents a tenfold change in acidity. Therefore, a solution with pH 3 is ten times more acidic than a solution with pH 4, and a hundred times more acidic than a solution with pH 5.

Following equilibrium is set up at 298 K in a 1 L flask.

If one starts with 2 moles of A and 1 mole of B, it is found that moles of B and D are equal.Thus Kc is 
  • a)
    9.0
  • b)
    15.0
  • c)
    3.0
  • d)
    0.0667
Correct answer is option 'B'. Can you explain this answer?

Sushil Kumar answered
For the equilibrium reaction:
A+2B ⇌ 2C+D
volume of flask = 1L
Initial moles of A = 2 mol
initial concentration of A=[A]i = 2 M
initial mole of B = 1 mol 
[B]i = 1 M
[A]eq = 2-x, [B]eq = 1-2x, [C]eq = x, [D]eq = 3x
Given [D]eq = 1 * 1L
= 1 M
Thus x = 1M
[A]eq = 1, [B]eq = -1, [C]eq = 1, [D] = 3
Kc = {([D]eq)3 * ([C]eq)}/{[A]eq * ([B]eq)2
= Kc = {(3)3*1}/{1*(-1)2}
= 27/1
= 27

The exothermic formaton of ClF3 is represented by the equation -
Cl2(g)+3F2(g) 2ClF3(g) ; ΔrH = -329 kJ
Which of the following will increase the quantity of ClF3 in an equilibrium mixture of Cl2, F2 and ClF3 ?
  • a)
    Removing Cl2
  • b)
    Increasing the temperature
  • c)
    Adding F2
  • d)
    Increasing the volume of the container
Correct answer is option 'C'. Can you explain this answer?

Hansa Sharma answered
The correct answer is option C
According to Le-Chatelier's Principle, if a system at equilibrium is subjected to a change of concentration pressure or temperature then the equilibrium is shifted in such a way as to nullify the effect of change.
In the given reaction, if the concentration of F2 is increased then the reaction will shift in the forward direction in order to increase the concentration of ClF3.
Hence, 
Adding F2 .

How many of the following are Lewis bases?
    Correct answer is '6'. Can you explain this answer?

    Pooja Shah answered
    Total number of compounds acting as Lewis base in the given example is 6. H+ and BF3 are electron deficient so they can't act as Lewis base while FeCl3 acts as Lewis acid so all the other compounds except these three are Lewis base.

    The pH of a 0.1 molar solution of the acid HQ is 3. The value of the ionization constant, Ka of this acid is - [AIEEE-2012]
    • a)
      1 × 10-3
    • b)
      1 × 10-5
    • c)
      1 × 10-7
    • d)
      3 × 10-1
    Correct answer is option 'B'. Can you explain this answer?

    Naina Bansal answered
    HQ will dissociate as 
    H2O + HQ ↔ H3O^+ + Q-
    Ka = [H3O^+] [Q-] / [HQ]
    -log [H3O^+] = pH
    - log [H3O^+] = 3
    [H3O^+] = 10^-3
    [H3O+] = [Q-] = 10-3
    Ka = ( 10^-3)^2 / (0.1 - 10^-3) = ( 10^-3)^2 / (0.1) = 1 x 10^-5

     In which of the following reaction can equilibrium be attained
    • a)
      Reversible reaction
    • b)
      Cyclic reaction
    • c)
      Decomposition reaction
    • d)
      Irreversible reaction
    Correct answer is option 'A'. Can you explain this answer?

    Rajat Kapoor answered
    Reversible Reaction
    The common observation for any reactions when they are reacted in closed containers would not go to completion, for some given conditions like temperature and pressure.
    For all those cases, only the reactants are found to be present in the intial stages, but with the progress of reaction, the reactants concentration decreases and to that of the products increases. A stage is finally reached where there is no more change of reactants and products concentration is observed. The state where the reactants and products concentrations do not show any visible change within a given period of time is better known as the state of chemical equilibrium. 
    The reactant amount that remains unused depends upon the experimental conditions like concentration of components, temperature of the system, pressure of the system and the reaction nature.

    Following equilibrium is set up at 1000 K and 1 bar in a 5 L flask,

    At equilibrium, NO2 is 50% o f the total volume. Thus, equilibrium constant Kc is 
    • a)
      0.133
    • b)
      0.266
    • c)
      0.200
    • d)
      0.400
    Correct answer is option 'A'. Can you explain this answer?

    The correct answer is Option A.    
                    N2O4  ⇌  2NO2
    Initial            1                 0           
    Equilibrium  1−x             2x
    Total moles = 1 - x + 2x 
    NO2 is 50% of the total volume when equilibrium is set up.
    Thus, the volume fraction (at equilibrium) of NO2 = 50/100 = 0.5 = ½
    So,    2x / (1+x) = ½
         => x = ⅓
    For 1 litre;
    Kc = [NO2] / [N2O4]
        = [4*(1/9)] / [⅔]
        = 0.66; 
    For 5 litres; 
    Kc = 0.66 / 5
    = 0.133
    Thus, option A is correct.
     

    Assume following equilibria when total pressure set up in each are equal to 1 atm, and equilibrium constant (Kp) as K1; K2 and K3


    Thus,
    • a)
       K1 = K2 = K3
    • b)
      K1 < K2 < K3
    • c)
      K3 < K2 < K1
    • d)
      None of these
    Correct answer is option 'C'. Can you explain this answer?

    The correct answer is option C
    CaCO3 ​→ CaO + CO2​
    Kp​ = k1 ​= Pco2​​
    total pressure of container P
    k1​ = p
    NH4​HS → NH3 ​+ H2​S
    PNH3​​ = PH2​S ​= P0​
    P0​ + P0​ = p (total pressure)
    P0 ​= p/2
    k2​ = kp ​= [PNH3​​][PH2​s​] p24
    NH2​CoNH2 ​→ 2NH3 ​+ CO2​
    PNH3​​ = 2P0​        PCO2​ ​= P0​
    2P0​ + P0 ​= P

    For HF, pKa = 3.45. What is the pH of an aqueous buffer solution that is 0.1M HF (aq) and 0.300 M KF (aq)?
    a)11.03
    b)2.97
    c)10.07
    d)3.93 
    Correct answer is option 'D'. Can you explain this answer?

    Suresh Iyer answered
    Given, pKa = 3.45
    Concentration of HF = 0.1 M, concentration of KF = 0.300 M
    For acidic buffer;
    pH = pKa + log [salt of weak acid]/[weak acid]
    = 3.45 + log0.3/0.1
    = 3.45 + 0.48
    = 3.93

    H2O (l) H2O(s) ; ΔH = -q
    Application of pressure on this equilibrium
    • a)
      cause formation of more ice
    • b)
      cause fusion of ice
    • c)
      has no effect
    • d)
      lower the melting point
    Correct answer is option 'B,D'. Can you explain this answer?

    Krishna Iyer answered
    The correct answers are Options B and D. 
     
    As we know that reaction is exothermic it means heat is released in the reaction so, if we apply pressure then reaction will proceed in backward direction but if there is gas phase equilibrium the reaction will shift in that direction in which less number of moles are present. If pressure increases then the ice will melt and ice gets more energy at low temp. To melt ,so it’s melting point decreases.
     

    The [Ag+(aq)] = 10-5 in a solution .The [Cl(aq)] to precipitate AgCl having Ksp of 1.8×10-10 M2 is — M
    • a)
      10-7
    • b)
      10-8
    • c)
      10-9
    • d)
      10-5
    Correct answer is option 'D'. Can you explain this answer?

    Hansa Sharma answered
    For precipitation, Qrkn > Ksp, then tto establish equilibrium, ions will combine to give molecule as ppt.
    So applying the above concept,
     1.8×10-10 < [Ag+][Cl-]
     1.8×10-10 < 10-5 × [Cl-]
    Or [Cl-] > 1.8×10-5
    By seeing the option, only option d satisfies this condtion.

    For the following electrochemical cell reaction at 298 K,
     
    E°cell = 1.10 V
    • a)
      0.027
    • b)
      37.22
    • c)
      0.012
    • d)
      85.73
    Correct answer is option 'B'. Can you explain this answer?

    Zn(s) + Cu2+(aq) ⇌ Cu(s) + Zn2+(aq),

    E= +1.10V

    ∴ Eo = 0.0591/n log10Keq
    because at equilibrium, 
    Ecell = 0

    (n = number of electrons exchanged = 2)

    1.10 = 0.0591/2 log10Keq
    2.20/0.0591 = log10Keq
    Keq = antilog37.225

    Solubility of BaCl2 if Ksp is 10-6 at 25°C is
    • a)
      Cannot be predicted
    • b)
      6.3 10-3 M
    • c)
      10-6 M
    • d)
      10-3 M
    Correct answer is option 'B'. Can you explain this answer?

    Ram Mohith answered
    BaCl₂ ⇔ Ba²⁺ + 2Cl⁻ Ksp = (s)(2s)² = 4s³ Given, 4s³ = 10⁻⁶ ⇒s³ = 0.25 ⨯ 10⁻⁶ ⇒s = (0.25)³ ⨯ 10⁻² ⇒s = 0.629 ⨯ 10⁻² ⇒s = 6.3 ⨯ 10⁻³

    We know that the relationship between Kc and Kp is Kp = Kc (RT)Δn
    What would be the value of Δn for the reaction NH4Cl (s) ⇔ NH3 (g) + HCl (g)
    a)1
    b)0.5
    c)1.5
    d)2
    Correct answer is option 'D'. Can you explain this answer?

    Nandini Patel answered
    The answer is d.
    The relationship between Kp and Kc is
    Kp = Kc (RT) ∆n
    Where ∆n = (number of moles of gaseous products) – (number of moles of gaseous reactants)
    For the reaction,
    NH4C1(s) ⇆ NH3(g) + HCl(g)
    ∆n = 2 – 0 = 2 

    In the following reaction,

    Species behaving as Bronsted-Lowry acids are
    • a)
      A,D
    • b)
      B,C
    • c)
      A,B
    • d)
      B,D
    Correct answer is option 'A'. Can you explain this answer?

    Om Desai answered
    Bronsted lowry acids are those acids which donate H+. In the reaction, A and D are giving H+. So, these both are bronsted lowry acid.

     In a buffer solution containing equal concentration of B and HB, the Kb for B is 10–10. The pH of buffer solution is : [2010]
    • a)
      10
    • b)
      7
    • c)
      6
    • d)
      4
    Correct answer is option 'D'. Can you explain this answer?

    Nilotpal Gupta answered
    For the buffer solution containing equal concentration of B and HB
    pH = pKa + log 1
    pH = pKa = 4
    The octahedral complex ion [ CoCl2(NH3)4]+ i.e., tetra amminedichloro cobalt (III) ion exists as cis and trans isomers.

    Kc forthe decomposition of NH4HS(s) is 1.8x 10-4 at 25°C.

    If the system already contains [NH3] = 0.020 M, then when equilibrium is reached, molar concentration are
    • a)
      a
    • b)
      b
    • c)
      c
    • d)
      d
    Correct answer is option 'B'. Can you explain this answer?

    Sushil Kumar answered
     NH4HS (s)  ⇋ NH3 (g) + H2S (g)
    Initial    1                   -               -
    At eqm     1-x                 x+0.02     x
    Kc = [NH3][H2S]   (Since NH4HS is solid, we ignore it.)
    1.8×10-4    = (x+0.02)(x)
    x2+0.02x-1.8×10-4 = 0
    Applying quadratic formula; x = -0.02+√{(0.02)2-4×1.8×10-4}
    = 0.033-0.020/2 = 0.0065
    Therefore, concn of NH3 at equilibrium = x+0.020 = 0.0265
    concn of H2S at equilibrium = x = 0.0065
    So, option b is correct

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