MDCAT/ECAT/FSC Grand Chemistry MCQs Quiz # 1| Interactive Quiz
1. Salt which is formed by the neutralization of weak acid and strong base is:
a
NaNO₃
Wrong
b
NH₄Cl
Wrong
c
Na₂CO₃
Right
d
NH₄CN
Wrong
Answer: (c)
Na₂CO₃ is formed from weak acid (H₂CO₃) and strong base (NaOH).
Na₂CO₃ is formed from weak acid (H₂CO₃) and strong base (NaOH).
2. Which one of the following cannot have value equal to zero?
a
Activation energy
Wrong
b
Reduction potential
Wrong
c
Principal quantum number
Wrong
d
Both a and c
Right
Answer: (d)
Activation energy cannot be zero (needs minimum energy to start reaction). Principal quantum number (n) starts from 1, cannot be zero.
Activation energy cannot be zero (needs minimum energy to start reaction). Principal quantum number (n) starts from 1, cannot be zero.
3. Which of the following enthalpy change is always negative?
a
∆Hแตฃ°
Wrong
b
∆Hf°
Wrong
c
∆Hc°
Right
d
∆Hd°
Wrong
Answer: (c)
∆Hc° (Enthalpy of Combustion) is always negative because combustion reactions are exothermic, meaning they release energy (heat) to the surroundings. In contrast, other enthalpy changes such as ∆Hf° (standard enthalpy of formation) and ∆Hแตฃ° (reaction enthalpy) can be either positive or negative depending on whether the process is exothermic or endothermic. ∆Hd° refers to enthalpy of decomposition, which can also be either exothermic or endothermic.
∆Hc° (Enthalpy of Combustion) is always negative because combustion reactions are exothermic, meaning they release energy (heat) to the surroundings. In contrast, other enthalpy changes such as ∆Hf° (standard enthalpy of formation) and ∆Hแตฃ° (reaction enthalpy) can be either positive or negative depending on whether the process is exothermic or endothermic. ∆Hd° refers to enthalpy of decomposition, which can also be either exothermic or endothermic.
4. The energy corresponds to the given thermochemical process is labeled as:
Li⁺ (g) + Cl⁻ (g) → LiCl(s)
a
Ionization energy
Wrong
b
Enthalpy of atomization
Wrong
c
Enthalpy of combustion
Wrong
d
Lattice energy
Right
Answer: (d)
Lattice energy is the energy released when gaseous ions (Li⁺ and Cl⁻) combine to form an ionic solid (LiCl). It reflects the strength of the ionic bond formed in the solid lattice.
Lattice energy is the energy released when gaseous ions (Li⁺ and Cl⁻) combine to form an ionic solid (LiCl). It reflects the strength of the ionic bond formed in the solid lattice.
5. In the equation of First law of thermodynamics (∆E=q + w), the property(s) which does not depend upon initial and final state is (are):
a
Ionization energy
Wrong
b
W
Wrong
c
q
Wrong
d
Both q and W
Right
Answer: (d)
∆E (change in internal energy) is a state function, meaning it depends only on the initial and final states of the system, not on the path taken. q (heat) and W (work) are path functions, meaning they depend on the process or path taken to go from the initial to the final state. Therefore, q and W do not only depend on the initial and final states, but on how the process occurs. Thus, q and W depend on the path, not just the initial and final states, making them the correct answer.
∆E (change in internal energy) is a state function, meaning it depends only on the initial and final states of the system, not on the path taken. q (heat) and W (work) are path functions, meaning they depend on the process or path taken to go from the initial to the final state. Therefore, q and W do not only depend on the initial and final states, but on how the process occurs. Thus, q and W depend on the path, not just the initial and final states, making them the correct answer.
6. The strongest oxidizing agent and strongest reducing agent in the electro chemical series respectively is:
a
Li and F
Wrong
b
Li and H₂
Wrong
c
F and Li
Right
d
H₂ and F
Wrong
Answer: (c)
F₂ (Fluorine) is the strongest oxidizing agent because it has the highest tendency to gain electrons and get reduced (as it has a very high reduction potential). Li (Lithium) is the strongest reducing agent because it has the highest tendency to lose electrons and get oxidized (it has the lowest reduction potential). Thus, F (as an oxidizing agent) and Li (as a reducing agent) are the strongest in their respective categories in the electrochemical series.
F₂ (Fluorine) is the strongest oxidizing agent because it has the highest tendency to gain electrons and get reduced (as it has a very high reduction potential). Li (Lithium) is the strongest reducing agent because it has the highest tendency to lose electrons and get oxidized (it has the lowest reduction potential). Thus, F (as an oxidizing agent) and Li (as a reducing agent) are the strongest in their respective categories in the electrochemical series.
7. Least entropy found in which of the following state of water:
a
Steam at 100°C
Wrong
b
Liquid water at 25°C
Wrong
c
Liquid water at 4°C
Wrong
d
Ice at 0°C
Right
Answer: (d)
Entropy is a measure of disorder or randomness. The least entropy is found in the solid state of water (ice) because the molecules are arranged in an orderly structure, leading to minimal disorder. As water moves from solid (ice) to liquid and then to gas (steam), the entropy increases due to more freedom of movement and disorder in the molecular arrangement. Therefore, ice at 0°C has the least entropy because the molecules are in a structured, fixed lattice, resulting in the lowest degree of disorder.
Entropy is a measure of disorder or randomness. The least entropy is found in the solid state of water (ice) because the molecules are arranged in an orderly structure, leading to minimal disorder. As water moves from solid (ice) to liquid and then to gas (steam), the entropy increases due to more freedom of movement and disorder in the molecular arrangement. Therefore, ice at 0°C has the least entropy because the molecules are in a structured, fixed lattice, resulting in the lowest degree of disorder.
8. Which of the following possesses weakest London dispersion forces:
a
Cl₂
Wrong
b
F₂
Right
c
Br₂
Wrong
d
I₂
Wrong
Answer: (b)
London dispersion forces (LDF) increase with the size and polarizability of the molecule. F₂ is the smallest molecule with the least number of electrons among the options, resulting in the weakest dispersion forces. As the size of the halogen molecule increases (Cl₂, Br₂, I₂), the number of electrons increases, which leads to stronger London dispersion forces.
London dispersion forces (LDF) increase with the size and polarizability of the molecule. F₂ is the smallest molecule with the least number of electrons among the options, resulting in the weakest dispersion forces. As the size of the halogen molecule increases (Cl₂, Br₂, I₂), the number of electrons increases, which leads to stronger London dispersion forces.
9. In NaCl, each Na ion is surrounded by CI ions in the numbers:
a
Four
Wrong
b
Three
Wrong
c
Six
Right
d
Seven
Wrong
Answer: (c)
In NaCl (sodium chloride), the structure is a face-centered cubic (FCC) lattice. Each Na⁺ ion is surrounded by 6 Cl⁻ ions in an octahedral arrangement, and vice versa. This means each ion in NaCl is coordinated to 6 oppositely charged ions.
In NaCl (sodium chloride), the structure is a face-centered cubic (FCC) lattice. Each Na⁺ ion is surrounded by 6 Cl⁻ ions in an octahedral arrangement, and vice versa. This means each ion in NaCl is coordinated to 6 oppositely charged ions.
10. Oxidation number of Cr in Na₂Cr₂O₇ is:
a
+6
Right
b
+12
Wrong
c
+7
Wrong
d
+5
Wrong
Answer: (a)
In Na₂Cr₂O₇, the total oxidation number of oxygen is -14 and sodium is +2. To balance this, each chromium (Cr) has an oxidation number of +6.
In Na₂Cr₂O₇, the total oxidation number of oxygen is -14 and sodium is +2. To balance this, each chromium (Cr) has an oxidation number of +6.