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:

Questions:

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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