Chemistry Test

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Chemistry Test - 10

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Weekly Quiz Competition

Question 1
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Directions: The following question has four choices out of which ONLY ONE is correct.

The enthalpy of neutralization of HCN by NaOH is - 12kJ/mol. The enthalpy of ionization of HCN is

A
- 12 KJ/ mol

B
69 KJ/ mol

C
12 KJ/ mol

D
- 45 KJ/ mol

Solution

The enthalpy of ionization of HCN is reverse of the enthalpy of neutralization of HCN. So enthalpy of ionization of HCN is 12 kJ/mol.
Question 2
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Directions: The following question has four choices out of which ONLY ONE is correct.

Dissolution of ammonium chloride in water is an endothermic change. At constant temperature, it is accompanied by

A
no change in enthalpy

B
decrease in entropy

C
no change in entropy

D
increase in entropy

Solution

Entropy in liquid state is more than that in solid state. So, dissolution of ammonium chloride in water is accompanied by increase in entropy.
Question 3
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If 150 kJ of energy is needed for a man to walk a distance of 1 km, then how much glucose does one have to consume to walk a distance of 5 km, provided that only 30% of energy is available for muscular work? (The enthalpy of combustion of glucose is 3000 kJ mol^-1.)

A
75 g

B
30 g

C
180 g

D
150 g

Solution
Question 4
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In which of the following cases is rate of reaction not affected by pressure?

A
PCl₃ (g) + Cl₂ (g) ⇌ PCl₅ (g)

B
N₂ (g) + 3H₂ (g) ⇌ 2NH₃ (g)

C
N₂ (g) + O₂ (g) ⇌ 2NO (g)

D
2SO₂ (g) + O₂ (g) ⇌ 2SO₂(g)

Solution

Since the number of moles of reactants and products are the same, there will not be any effect of pressure on the reaction.
Question 5
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Consider the following reactions:

NO₂ ⇌ N₂ + O₂, K₁

N₂O₄ ⇌ 2NO₂, K₂

Give the equilibrium constant for the formation of N₂O₄ from N₂ and O₂.

A

B

C

D

Solution
Question 6
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In 2HI ⇌ H₂ + I₂, the equilbrium is not affected by:

A
number of moles of reactants

B
pressure

C
volume

D
temperature

Solution

Since the numbers of moles of reactants and products are the same, there will not be any effect of pressure on the equilibrium.
Question 7
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What is the relation between K_p and K_c in the following reaction?

N₂(g) + 3H₂(g) 2NH₃(g)

A
K_p = K_c

B
K_p = K_c - RT

C
K_p = K_c/(RT)²

D
K_p = K_c/(RT)^-2

Solution
Question 8
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The favourable conditions for Haber's process are:

A
Low temperature and low pressure

B
Low temperature and high pressure

C
High temperature and low pressure

D
High temperature and high pressure

Solution

The favourable conditions for Haber's process are low temperature and high pressure, as:

(1) According to Le Chatelier's principle, low temperature will shift the equilibrium to the right because the reaction is exothermic.

(2) High pressure on the reaction at equilibrium favours the shift of the equilibrium to the right because the forward reaction proceeds with a decrease in the number of gaseous moles.
Question 9
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For the following reaction, 1 g mole of CaCO₃ is enclosed in a 5 L container.

CaCO₃ (s) CaO (s) + CO₂ (g)

Kp = 1.16 at 1073 K

The percent dissociation of CaCO₃ in the above reaction is

A
65%

B
100%

C
6.5%

D
zero

Solution
Question 10
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If at any temperature, Kp is the equilibrium constant for the reaction N₂ (g) + 3H₂ (g) ⇌ 2 NH₃(g), then what will be the effect of increasing the pressure from 5 atm to 50 atm?

A
Increase in the yield of ammonia as well as the value of K_p

B
Increase in the yield of NH₃, but no change in the value of K_p

C
Decrease in the yield of NH₃ as well as the value of K_p

D
Decrease in the yield of ammonia as well as the value of K_c

Solution

Since the number of moles of reactants is more than that of products, increasing pressure will increase the yield of NH₃ as well as the value of K_p.