Chemical Equilibrium Worksheet

Chemical Equilibrium occurs only on reversible reaction. After finding that some chemical reaction are reversible, the concept of chemical equilibrium was developed.

The law of chemical equilibrium shows the direction of chemical reaction and also defines the quantities of reactant and products that will remain after the reaction is complete.

Here, you can find some questions related to “Chemical Equilibrium” and their answers:


1. The active mass of 2 g. hydrogen kept in a 2 litre flask is:

(a)    2 mole / litre

(b)   0.5 mole/litre

(c)    3 mole/litre

(d)   None of these


2. Which one among the following reactions would not be reversible:

(a)    N_2 + 3H_2 = 2NH_3

(b)   CaCO_3 = CaO + CO

(c)    H_2 + I_2 = 2HI

(d)   AgNO_3 + NaCl = NaNO_3 + AgCl


3.  A gas cylinder provided with a piston, has some PCl_5 which is in equilibrium with Cl_2 \text{and} PCI_3 formed by its dissociation. Now the system is compressed with the help of the piston. Indicate the correct statement.

(a)    The system will remain unaffected

(b)   Some Cl_2 \text{and} PCI_3 present initially will combine to give more of PCI_5

(c)    Some PCl_5 will decompose to give more of chlorine

(d)   Some more PC15 will decompose to give Cl_2 \text{and} PCl_3


4. The factor with which equilibrium constant of the reaction H_2(g) + I_2(g) \leftrightharpoons 2HI(g) changes is:

(a)    Catalyst

(b)   Amount of H_2 \text{and} I_2

(c)    Total pressure

(d)   Temperature


5. The equilibrium state is characterised by:

(a)    Decrease of entropy

(b)   Increase of internal energy

(c)    Increase of entropy

(d)   None of these


6. In a spontaneous change, the system undergoes:

(a)    No change in energy

(b)   Increase in internal energy

(c)    Decrease of pressure

(d)   Decrease in free energy


7. For the system, A(g) + 2B(g) \leftrightharpoons C(g)  the concentrations are:

[A] = 0.06 mole /L, [B] = 0.12 mole /L and [C] = 0.216 mole /L.

The value of K_c for the reaction is:

(a)    250

(b)   127

(c)    418

(d)   4 \times 10^{-3}


8. When NH_4Cl is dissolved in water, the solution shows a cooling effect. The solubility of NH4Cl will:

(a)    Increase on increasing temperature

(b)   Remain independent of temperature change

(c)    Decrease on increase temperature

(d)   None of these


9. The yield of product in the reaction, A_2(g) + 2B(g) \leftrightharpoons K(g) + Q kJ would be higher at:

(a)    Low temperature and low pressure

(b)   High temperature and high pressure

(c)    Low temperature and high

(d)   High temperature and low pressure


10. HI was heated in a sealed tube at 440^0C, till the equilibrium was reached. HI was found be 22% dissociated. The equilibrium constant for dissociation is:

(a)    0.282

(b)   1.99

(c)    0.0869

(d)   0.0198


11. The equilibrium constant in a reversible reaction a given temperature:

(a)    Is not characteristic of the reaction

(b)   Depends on the initial concentration of the reactants

(c)    Does not depend on the initial concentrations

(d)   Depends on the concentration of the products at equilibrium


12. At constant temperature when the concentration of a reactant is increased, the equilibrium constant:

(a)    Decreases

(b)   First increases and then decreases

(c)    Remains unaffected

(d)   Increases


13. Given the reaction, 2 x (g) + Y (g) \leftrightharpoons Z(g)80 kcals. Which combination of pressure and temperature gives the highest yield of Z at equilibrium ?

(a)    600 atm. And 500 ^0 C

(b)   500 atm. And 100^0 C

(c)  1000 atm. And 100^0 C

(d)  ]1000 atm. And 500^0 C


14. 1 mole of H_2 and 2 moles of I_2 are taken initially in 2-litre vessel. If the number of moles of H_2 at equilibrium is 0.2. the number of moles of I_2 \text{and} HI, respectively, at equilibrium would be:

(a)    1.2,1.e

(b)   0.8, 2.8

(c)    1.8,1.0

(d)   0.4, 2.4


15. Consider the equilibrium

CO_2 (g) \leftrightharpoons CO(g) + \dfrac{1}{2}O_2 (g)

The equilibrium constant K is given by (when a << 1)

(a)    K =\dfrac{a^{3/2}}{\sqrt{2}}

(b)   \dfrac{a^3}{2}

(c)    K = \dfrac{a^{3/2}}{2}

(d)   K = \dfrac{a^{3/2}}{\sqrt{3}}


16. For he equilibrium NH_4HS (s) \leftrightharpoons NH_3 (g) + H_2S (g), will be shifted to the right when:

(a)    Q = K_p

(b)   Q < K_p

(c)    Q < 2K_p

(d)   K_p > 1


17. In which of the following chemical reaction at equilibrium is K_p \neq K_c ?

(a)    PCl_5 (g) \leftrightharpoons PCl (g) + Cl_2 (g)

(b)   N_2O_5 (g) \leftrightharpoons 2NO_2(g)

(c)    2SO_2 (g) + O_2 (g) \leftrightharpoons 2SO_3 (g)

(d)   All of these


18. The vapour density of completely dissociated N_2 O_4 would be:

(a)    Double that of N_2O

(b)   Half that of N_2O_4

(c)    Greater than half that of N_2 O_4

(d)   Less than half that of N_2O_4


19. In the reaction C(s) + CO_2(g) \leftrightharpoons 2CO(g), equilibrium pressure is 12 atm. If 50% of the CO_2 reacts, the value of K_p will be:

(a)    32

(b)   13

(c)    16

(d)   17


20. Van’t Hoff equation giving the effect of temperature on chemical equilibrium is represented as:

(a)    \dfrac{d ln F}{dT} = \dfrac{\Delta H}{RT^2}

(b)   \dfrac{d ln k_P}{dT} = \dfrac{RT^2}{\Delta H}

(c)    \dfrac{d ln K_p}{dT} = \dfrac{\Delta HT^2}{R}

(d)   \dfrac{d ln K_p}{dT} = \dfrac{\Delta H}{RT^2}


21. In the system, CaF_2(s) \leftrightharpoons Ca^{2+} + 2F^-  increasing the concentration of Ca^{2+} ions 4 times will cause the equilibrium concentration of F^- ions to change to:

(a)    2 times of the initial

(b)   1/4 of the initial value

(c)    2 times of the initial value

(d)   None


22. If \Delta G^0 for the reaction given below is 1.7 kJ; the equilibrium constant of the reaction,

2HI (g) \leftrightharpoons H_2 + I_2 (g) at 298 K is:

(a)    2.6

(b)   3.8

(c)    20.4

(d)   0.5


23. In which case the reaction is farthest from completion?

(a)    K_c = 10^3

(b)   K_c = 10

(c)    K_c = 10^4

(d)   K_c = 10^{-8}


24. If K_p for the reaction P + 2Q \leftrightharpoons 3R + S is 0.05 at 1000 K then

Find K_c for this reaction?

(a)    5 \times 10^{-4} R

(b)   \dfrac{5 \times 10^{-5}}{R}

(c)    0.002R

(d)   5 \times 10^{-5}R


25. Which is correct relation here?

(a)    K_C = K_p(RT)^{\Delta n}

(b)   K_p = K_C /RT^{\Delta N}

(c)    \Delta G^0 = -2.303 R \log

(d)   \Delta G^0 = -2.303 RT \log K


1.(b)          2. (d)           3. (b)           4. (d)           5. (c)

6. (d)         7. (a)           8. (a)           9. (c)          10. (a)

11. (c)        12. (c)         13. (c)          14. (a)         15. (a)

16. (b)        17. (d)        18. (b)         19. (c)        20. (d)

21. (c)         2. (d)          23. (d)        24. (b)        25. (d)

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