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chemistry MCQs

11th • Chapter 08

49 Questions TextBook
1

A reaction that proceeds in both forward and reverse directions is called a?

A
Reversible reaction
B
Irreversible reaction
C
Spontaneous reaction
D
Non-spontaneous reaction
2

Which of the following is an example of an irreversible reaction at normal temperature?

A
N2(g) + 3H2(g) <=> 2NH3(g)
B
H2(g) + I2(g) <=> 2HI(g)
C
2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g)
D
PCl5(g) <=> PCl3(g) + Cl2(g)
3

At what temperature does the decomposition of H2O become noticeable?

A
100°C
B
500°C
C
1000°C
D
1500°C
4

In the Haber process for ammonia synthesis, what is the catalyst used?

A
Platinum
B
Iron
C
Vanadium pentoxide
D
Nickel
5

A state of chemical equilibrium is achieved when?

A
Concentrations of reactants and products become equal
B
Rates of forward and reverse reactions become equal
C
The reaction stops completely
D
The temperature of the system becomes constant
6

According to the law of mass action, the rate of a chemical reaction is directly proportional to the?

A
Product of the active masses of the products
B
Sum of the active masses of the reactants
C
Product of the active masses of the reactants
D
Sum of the active masses of the products
7

The term 'active mass' represents the concentration in which units?

A
grams dm⁻³
B
moles dm⁻³
C
kg dm⁻³
D
grams cm⁻³
8

For the reaction aA + bB <=> cC + dD, the equilibrium constant Kc is expressed as?

A
[C]c[D]d / [A]a[B]b
B
[A]a[B]b / [C]c[D]d
C
[C][D] / [A][B]
D
[A][B] / [C][D]
9

When does the equilibrium constant Kc have no units?

A
When the number of moles of reactants is greater than products
B
When the number of moles of products is greater than reactants
C
When the number of moles of reactants and products are equal
D
Kc always has units
10

What is the unit of Kc for the reaction N2(g) + 3H2(g) <=> 2NH3(g)?

A
mol⁻² dm⁶
B
mol² dm⁻⁶
C
mol dm⁻³
D
No units
11

In the esterification reaction CH3COOH(aq) + C2H5OH(aq) <=> CH3COOC2H5(aq) + H2O(l), how does a change in volume affect the Kc value?

A
Increases Kc
B
Decreases Kc
C
Does not affect Kc
D
Doubles Kc
12

For the dissociation of PCl5, Kc = x² / V(a-x). What does 'x' represent?

A
Initial moles of PCl5
B
Moles of PCl5 at equilibrium
C
Moles of PCl5 decomposed
D
Volume of the container
13

The relationship between Kp and Kc is given by the equation?

A
Kp = Kc(RT)Δn
B
Kc = Kp(RT)Δn
C
Kp = Kc(R/T)Δn
D
Kp = Kc + RTΔn
14

In the synthesis of NH3, N2(g) + 3H2(g) <=> 2NH3(g), what is the value of Δn?

A
2
B
-2
C
1
D
-1
15

If the [products]/[reactants] ratio is less than Kc, in which direction will the reaction proceed?

A
Forward direction
B
Reverse direction
C
It is at equilibrium
D
The reaction will stop
16

A very large value of Kc (e.g., 10⁵⁵) indicates that?

A
The reaction is very slow
B
The reaction does not proceed in the forward direction
C
The reaction is almost complete
D
The reaction is at equilibrium
17

Le-Chatelier's principle states that if a stress is applied to a system at equilibrium, the system will act to?

A
Maximize the stress
B
Nullify the effect of the stress
C
Completely ignore the stress
D
Stop the reaction
18

For the reaction BiCl3 + H2O <=> BiOCl + 2HCl, what happens if HCl is added to the equilibrium mixture?

A
The reaction shifts forward
B
The reaction shifts backward
C
No change occurs
D
BiOCl precipitates more
19

For which type of reaction is the effect of pressure change significant?

A
Reactions in solution
B
Gaseous reactions with equal moles on both sides
C
Gaseous reactions with unequal moles on both sides
D
Solid-phase reactions
20

For the exothermic reaction 2SO2(g) + O2(g) <=> 2SO3(g), how does an increase in temperature affect the equilibrium?

A
Shifts it to the right
B
Shifts it to the left
C
No effect
D
Increases the value of Kp
21

What is the effect of a catalyst on a reversible reaction?

A
It increases the yield of products
B
It shifts the equilibrium to the right
C
It increases the rates of both forward and reverse reactions
D
It changes the value of Kc
22

What are the optimum conditions for the Haber's process?

A
High pressure, high temperature
B
Low pressure, low temperature
C
High pressure, moderate temperature, catalyst
D
Low pressure, high temperature, catalyst
23

In the Contact process, the conversion of SO2 to SO3 is an exothermic reaction. A high yield of SO3 is favored by?

A
High temperature and low pressure
B
Low temperature and high pressure
C
High temperature and high pressure
D
Low temperature and low pressure
24

The ionic product of water, Kw, at 25°C is?

A
1.0 x 10⁻⁷
B
1.0 x 10⁻¹⁴
C
1.8 x 10⁻¹⁶
D
55.5
25

What is the pH of a neutral solution at 25°C?

A
0
B
14
C
7
D
1
26

The term pH was introduced by?

A
Guldberg and Waage
B
Le Chatelier
C
Sorenson
D
Bronsted
27

A solution with a pH < 7 is considered?

A
Acidic
B
Basic
C
Neutral
D
A buffer
28

The sum of pH and pOH at 25°C is always equal to?

A
7
B
0
C
1
D
14
29

The dissociation constant of a weak acid is represented by?

A
Kw
B
Kc
C
Ka
D
Kb
30

A weak acid is one that has a Ka value?

A
Greater than 1
B
Equal to 1
C
Less than 10⁻³
D
Equal to Kw
31

The percentage ionization of a weak acid increases with?

A
Increasing concentration
B
Decreasing temperature
C
Dilution
D
Adding a common ion
32

The product of Ka of an acid and Kb of its conjugate base is equal to?

A
1
B
14
C
Kw
D
Ka / Kb
33

The suppression of ionization of a weak electrolyte by adding a common ion is called?

A
Salt effect
B
Common ion effect
C
Buffer effect
D
Hydrolysis
34

A buffer solution resists changes in?

A
Temperature
B
Pressure
C
Volume
D
pH
35

An acidic buffer is prepared by mixing a weak acid with?

A
a strong acid
B
a strong base
C
its salt with a strong base
D
its salt with a weak base
36

The pH of a buffer solution can be calculated using the?

A
Henderson's equation
B
Dalton's law
C
Law of mass action
D
Arrhenius equation
37

The best buffer is prepared by taking?

A
Higher concentration of acid than salt
B
Higher concentration of salt than acid
C
Equal concentrations of salt and acid
D
Very low concentrations of both
38

The solubility product, Ksp, is the product of the molar concentrations of ions in a?

A
Dilute solution
B
Concentrated solution
C
Saturated solution
D
Unsaturated solution
39

If the ionic product of a solution is greater than its Ksp, what will happen?

A
More salt will dissolve
B
The solution becomes unsaturated
C
Precipitation will occur
D
The solution is at equilibrium
40

The presence of a common ion ________ the solubility of a slightly soluble ionic compound.

A
increases
B
decreases
C
does not affect
D
doubles
41

In the reaction 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g), the reverse reaction is considered?

A
Negligible at normal temperature
B
Very fast at normal temperature
C
Favorable at high temperature
D
Equally likely as the forward reaction
42

What happens to the concentrations of reactants and products when a reversible reaction reaches equilibrium?

A
They become zero
B
They become equal
C
They become constant
D
They continuously change
43

The law of mass action was derived by?

A
Le Chatelier
B
Haber
C
C.M. Guldberg and P. Waage
D
Sorenson
44

What is the value of Kp if Kc is 6.0 x 10⁻² at 500°C for the reaction N₂(g) + 3H₂(g) ⇌ 2NH₃(g)? (R=0.0821)

A
1.5 x 10⁻⁵
B
6.0 x 10⁻²
C
2.5 x 10³
D
4.0 x 10⁻¹
45

For the reaction 2O₃(g) ⇌ 3O₂(g), Kc = 10⁵⁵ at 25°C. This implies that?

A
O₃ is very stable
B
The forward reaction is very slow
C
O₃ decomposes very rapidly to O₂
D
The reverse reaction is favored
46

A solution has a pOH of 11. What is its pH at 25°C?

A
11
B
7
C
3
D
14
47

What is the conjugate base of the acid HA?

A
H₂O
B
H₃O⁺
C
A⁻
D
OH⁻
48

For the best buffer capacity, the ratio of [salt]/[acid] should be close to?

A
10
B
0.1
C
100
D
1
49

The solubility of which salt is NOT significantly affected by a change in temperature?

A
KI
B
LiCl
C
NaCl
D
KClO₃