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NEET Chemistry

Chemistry questions for NEET UG — Physical, Organic, Inorganic Chemistry.

41 Q 1 Topics Take Test

Difficulty: All Easy Medium Hard 21–30 of 41

Topics in NEET Chemistry

All Physical Chemistry 88

Q.21 Medium Physical Chemistry

In electrochemistry, what does the cell potential (E°cell) indicate?

A The voltage of the battery

B The maximum work that can be obtained from the cell

C The rate of the reaction

D The concentration of electrolyte

Correct Answer: B. The maximum work that can be obtained from the cell

EXPLANATION

E°cell is directly related to the maximum electrical work (w_max = -nFE°cell) that can be obtained from a galvanic cell.

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Q.22 Medium Physical Chemistry

The hydration enthalpy of an ion depends on which of the following factors?

A Charge and size of the ion only

B Only the temperature

C Only the solvent used

D Pressure and temperature

Correct Answer: A. Charge and size of the ion only

EXPLANATION

Hydration enthalpy depends on the charge density of the ion (charge/size ratio). Higher charge and smaller size lead to greater hydration enthalpy.

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Q.23 Medium Physical Chemistry

For the equilibrium PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), Kc = 1.8 at 298 K. If initial concentration of PCl₅ is 1 M, find [PCl₃] at equilibrium when dissociation is 30%.

A 0.3 M

B 0.7 M

C 0.6 M

D 0.9 M

Correct Answer: A. 0.3 M

EXPLANATION

If 30% of PCl₅ dissociates, [PCl₃] = 1 × 0.30 = 0.3 M and [Cl₂] = 0.3 M.

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Q.24 Medium Physical Chemistry

The rate of reaction doubles when temperature increases from 300 K to 310 K. Calculate the activation energy (Ea) using Arrhenius equation.

A 52.8 kJ/mol

B 52.8 J/mol

C 105.6 kJ/mol

D 26.4 kJ/mol

Correct Answer: A. 52.8 kJ/mol

EXPLANATION

Using ln(k₂/k₁) = (Ea/R)(T₂-T₁)/(T₁T₂), ln(2) = (Ea/8.314)(10)/(93000). Solving: Ea ≈ 52.8 kJ/mol.

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Q.25 Medium Physical Chemistry

In a galvanic cell, if ΔG° = -95.5 kJ/mol and n = 2, what is E°cell? (F = 96500 C/mol)

A 0.495 V

B 0.990 V

C 0.248 V

D 1.98 V

Correct Answer: A. 0.495 V

EXPLANATION

ΔG° = -nFE°, so E° = -ΔG°/(nF) = 95500/(2 × 96500) = 0.495 V

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Q.26 Medium Physical Chemistry

For a weak acid HA with concentration 0.1 M and Ka = 4 × 10⁻⁶, the degree of ionization is:

A 0.002

B 0.0063

C 0.002%

D 0.2%

Correct Answer: B. 0.0063

EXPLANATION

α = √(Ka/C) = √(4×10⁻⁶/0.1) = √(4×10⁻⁵) = 0.0063 or 0.63%

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Q.27 Medium Physical Chemistry

The standard entropy change (ΔS°) for vaporization of water at 100°C and 1 atm is 108.8 J/(mol·K). What is ΔG° at 100°C?

A 0 J/mol

B -108.8 J/mol

C 108.8 J/mol

D 54.4 J/mol

Correct Answer: A. 0 J/mol

EXPLANATION

At phase transition equilibrium, ΔG° = ΔH° - TΔS° = 0 because the process is reversible

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Q.28 Medium Physical Chemistry

For the reaction: PCl₅(g) ⇌ PCl₃(g) + Cl₂(g), if initial pressure of PCl₅ is 1 atm and degree of dissociation is 0.4, what is Kp at constant total pressure?

A 0.267 atm

B 0.444 atm

C 0.889 atm

D 1.333 atm

Correct Answer: A. 0.267 atm

EXPLANATION

Initial: PCl₅ = 1 atm. At equilibrium with α = 0.4: PCl₅ = 0.6, PCl₃ = 0.4, Cl₂ = 0.4 atm. Kp = (0.4 × 0.4)/(0.6) = 0.267 atm

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Q.29 Medium Physical Chemistry

The Born-Landé equation is used to calculate which property?

A Ionization energy

B Lattice energy

C Bond dissociation energy

D Electron affinity

Correct Answer: B. Lattice energy

EXPLANATION

Born-Landé equation specifically calculates lattice energy of ionic compounds based on ionic radii and charges

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Q.30 Medium Physical Chemistry

An ideal gas undergoes isothermal compression from 10 L to 5 L at constant temperature. The work done ON the gas is:

A Positive

B Negative

C Zero

D Cannot be determined

Correct Answer: A. Positive

EXPLANATION

In compression, volume decreases and work is done ON the gas, making w positive (in physics convention). W = -nRT ln(Vf/Vi) where Vf < Vi

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