Chemistry Test 199

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Chemistry Test 199

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Weekly Quiz Competition

Question 1
4 / -1

A sample of HI (g) is placed in flask at a pressure of 0.2 atm. At equilibrium the partial pressure of HI (g) is 0.04 atm. What is K_p for the given equilibrium?

A
6

B
16

C
4

D
2

Solution
Question 2
4 / -1

An amount of solid NH₄HS is placed in a flask already containing ammonia gas at a certain temperature and 0.50 atm pressure. Ammonium hydrogen sulphide decomposes to yield NH₃ and H₂S gases in the flask. When the decomposition reaction reaches equilibrium the total pressure in the flask rises to 0.84 atm? The equilibrium constant for NH₄HS decomposition at this temperature is:

A
0.11

B
0.17

C
0.18

D
0.30

Solution
Question 3
4 / -1

Which of the following conclusions is correct for a certain reaction whose K_c is 2 × 10⁻³ at 25°C and 2 × 10⁻² at 50°C?

A
ΔH = +ve

B
ΔH = −ve

C
ΔH = 0

D
Both (b) and (c)

Solution

The given data suggests an increase in the value of K with an increase in the temperature. This case is true for endothermic reactions. For such reactions, the enthalpy of products is more than the enthalpy of the reactants and thus the sign of ∆H will be positive.
Question 4
4 / -1

A reaction system in equilibrium according to reaction 2SO₂(g) + O₂(g) ⇌ 2SO₃(g) in one litre vessel at a given temperature was found to be 0.12 mole each of SO₂ and SO₃ and 5 mole of O₂. In another vessel of one litre contains 32 g of SO₂ at the same temperature. What mass of O₂ must be added to this vessel to order that at equilibrium 20% of SO₂ is oxidized to SO₃?

A
0.4125 g

B
11.6 g

C
1.6 g

D
None of these

Solution
Question 5
4 / -1

For a reaction at equilibrium, which of the following statements is correct?

A
Concentration of reactant is equal to concentration of product

B
Concentration of reactant is always greater than product

C
Rate of forward reaction = rate of backward reaction

D
Q_c ≥ K

Solution

At chemical equilibrium, rate of forward reaction is equal to the rate of backward reaction.
Question 6
4 / -1

For the reaction, PCl₃ (g)+Cl₂ (g) ⇌ PCl₅ (g) the position of equilibrium can be shifted to the right by

A
doubling the volume.

B
increasing the temperature.

C
addition of equimolar quantities of PCl₃ and PCl₅.

D
addition of Cl₂ at constant volume.

Solution

PCl₃ (g)+Cl₂ (g) ⇌ PCl₅ (g)

According to Le-Chatelier's principle, on increasing the volume of a reactant, the reaction proceeds in the forward direction. Hence, on addition of Cl₂ to above reaction, the equilibrium will shift to the right.
Question 7
4 / -1

Which of the following statements is correct?

A
At equilibrium, the concentration of each of the reactant and product becomes equal.

B
At equilibrium, the r_f ≠ r_b, hence equilibrium is static in nature.

C
A chemical equilibrium can be established only if none of the products is allowed to separate out as solid from solution.

D
Chemical equilibrium can be attained only in one direction.

Solution

At equilibrium, the concentration of reactants and products may or may not become equal, but it becomes constant, i.e., there occurs no further change in the concentration of reactants and products.

Also, the rate of the forward reaction is equal to the rate of backward reaction: r_f = r_b. This is the state of dynamic equilibrium.

Equilibrium can be attained from both sides, whether we start from reactants or the products.

While, if there is any formation of precipitate in the reaction, the reaction no longer remains in the state of equilibrium and the reaction becomes unidirectional.
Question 8
4 / -1

In a chemical reaction, the rate constant for the backward reaction is 7.5 × 10^–4 and the equilibrium constant is 1.5. The rate constant for the forward reaction is -

A
5 × 10^–4

B
2 × 10^–3

C
1.125 × 10^–3

D
9.0 × 10^–4

Solution

Apply the formula, K = K_f/K_b

we get, K_f= 1.5 × 7.5 × 10⁻⁴= 1.125 × 10⁻³
Question 9
4 / -1

At constant temperature, the equilibrium constant (K_p) for the decomposition reaction N₂O₄⇌ 2NO₂ is expresses by where P = pressure, x = extent of decomposition. Which one of the following statements is true?

A
K_p increases with increase of P

B
K_p increases with increase of x

C
K_p increases with decrease of x

D
K, remains constant with change in P and x

Solution

The reaction proceeds with an increase in volume.

So, an increase in pressure (P) favours the reaction in the backward direction.

Thus, Kp remains constant with change in P and x.
Question 10
4 / -1

For the reaction, CO(g) + Cl₂(g) ⇌ COCl₂(g), the value of K_p/K_c is equal to:

A
1/RT

B
RT

C

D
1.0

Solution

K_p = K_c(RT)^Δn

Δ_n = Number of gaseous molecule of products − Number of gaseous molecules of reactants

CO(g) + Cl₂(g) → COCl₂(g)

∴ Δn = 1 − 2 = −1

∴ K_p = K_c(RT)⁻¹

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Chemistry Test 199

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Chemistry Test 199

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SHARING IS CARING

Question 1

6

16

4

2

Solution

Question 2

0.11

0.17

0.18

0.30

Solution

Question 3

ΔH = +ve

ΔH = −ve

ΔH = 0

Both (b) and (c)

Solution

Question 4

0.4125 g

11.6 g

1.6 g

None of these

Solution

Question 5

Concentration of reactant is equal to concentration of product

Concentration of reactant is always greater than product

Rate of forward reaction = rate of backward reaction

Qc ≥ K

Solution

Question 6

doubling the volume.

increasing the temperature.

addition of equimolar quantities of PCl3 and PCl5.

addition of Cl2 at constant volume.

Solution

Question 7

At equilibrium, the concentration of each of the reactant and product becomes equal.

At equilibrium, the rf ≠ rb, hence equilibrium is static in nature.

A chemical equilibrium can be established only if none of the products is allowed to separate out as solid from solution.

Chemical equilibrium can be attained only in one direction.

Solution

Question 8

5 × 10–4

2 × 10–3

1.125 × 10–3

9.0 × 10–4

Solution

Question 9

Kp increases with increase of P

Kp increases with increase of x

Kp increases with decrease of x

K, remains constant with change in P and x

Solution

Question 10

1/RT

RT

1.0

Solution

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Q_c ≥ K

addition of equimolar quantities of PCl₃ and PCl₅.

addition of Cl₂ at constant volume.

At equilibrium, the r_f ≠ r_b, hence equilibrium is static in nature.

5 × 10^–4

2 × 10^–3

1.125 × 10^–3

9.0 × 10^–4

K_p increases with increase of P

K_p increases with increase of x

K_p increases with decrease of x