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NEET UG

NEET UG MCQ questions — Physics, Chemistry, Botany & Zoology for medical entrance.

904 Q 4 Subjects 12th (PCB)
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Difficulty: All Easy Medium Hard 21–30 of 904
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Q.21 Hard NEET Chemistry Physical Chemistry
The decomposition of H₂O₂ follows first-order kinetics with k = 0.01 s⁻¹. If initial concentration is 0.1 M, what will be the concentration after 100 seconds?
A 0.0368 M
B 0.0050 M
C 0.0001 M
D 0.0002 M
Correct Answer:  A. 0.0368 M
EXPLANATION

For first-order: [A] = [A₀]e^(-kt) = 0.1 × e^(-0.01×100) = 0.1 × e^(-1) = 0.1 × 0.368 = 0.0368 M

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Q.22 Medium NEET Chemistry Physical Chemistry
For a spontaneous process at constant temperature and pressure:
A ΔG > 0 and ΔS > 0
B ΔG < 0 and ΔH > 0
C ΔG < 0 and ΔS > 0
D ΔG = 0 and ΔH = 0
Correct Answer:  C. ΔG < 0 and ΔS > 0
EXPLANATION

For spontaneous process: ΔG < 0. Generally also ΔS > 0 for most spontaneous processes. (ΔH < 0 is not always required)

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Q.23 Medium NEET Chemistry Physical Chemistry
The solubility product of AgCl at 25°C is 1.8 × 10⁻¹⁰. What is the solubility in mol/L?
A 1.34 × 10⁻⁵
B 2.68 × 10⁻⁵
C 4.24 × 10⁻⁵
D 9 × 10⁻⁶
Correct Answer:  A. 1.34 × 10⁻⁵
EXPLANATION

For AgCl: Ksp = [Ag⁺][Cl⁻] = s² = 1.8 × 10⁻¹⁰. s = √(1.8 × 10⁻¹⁰) = 1.34 × 10⁻⁵ mol/L

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Q.24 Medium NEET Chemistry Physical Chemistry
At 25°C, for the reaction: Cu²⁺(aq) + Zn(s) → Cu(s) + Zn²⁺(aq), E° = 1.1 V. What is ΔG°? (F = 96500 C/mol)
A -212.3 kJ/mol
B -106.15 kJ/mol
C -424.6 kJ/mol
D -53.075 kJ/mol
Correct Answer:  A. -212.3 kJ/mol
EXPLANATION

ΔG° = -nFE° = -2 × 96500 × 1.1 = -212300 J/mol = -212.3 kJ/mol

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Q.25 Medium NEET Chemistry Physical Chemistry
In a galvanic cell, at the cathode:
A Oxidation occurs and it's the positive electrode
B Reduction occurs and it's the negative electrode
C Reduction occurs and it's the positive electrode
D Oxidation occurs and it's the negative electrode
Correct Answer:  C. Reduction occurs and it's the positive electrode
EXPLANATION

Cathode is where reduction occurs. It's the positive electrode in a galvanic cell as it attracts cations.

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Q.26 Medium NEET Chemistry Physical Chemistry
A buffer solution is prepared by mixing 100 mL of 0.1 M CH₃COOH and 100 mL of 0.1 M CH₃COONa. The pKa of acetic acid is 4.74. What is the pH?
A 3.74
B 4.74
C 5.74
D 6.74
Correct Answer:  B. 4.74
EXPLANATION

Using Henderson-Hasselbalch: pH = pKa + log([A⁻]/[HA]) = 4.74 + log(0.1/0.1) = 4.74

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Q.27 Medium NEET Chemistry Physical Chemistry
For the exothermic reaction: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), increasing temperature will:
A Increase Kc and shift equilibrium right
B Decrease Kc and shift equilibrium left
C Increase Kc and shift equilibrium left
D No effect on equilibrium
Correct Answer:  B. Decrease Kc and shift equilibrium left
EXPLANATION

For exothermic reactions, increasing temperature decreases Kc (unfavorable) and shifts equilibrium left (Le Chatelier's principle).

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Q.28 Medium NEET Chemistry Physical Chemistry
The osmotic pressure of a solution is given by π = iMRT. If 0.1 M glucose solution has osmotic pressure 2.46 atm at 273 K, what is the van't Hoff factor?
A 0.5
B 1
C 2
D 4
Correct Answer:  B. 1
EXPLANATION

i = π/(MRT) = 2.46/(0.1 × 0.0821 × 273) ≈ 1. Glucose is non-electrolyte with i = 1

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Q.29 Easy NEET Chemistry Physical Chemistry
When 50 mL of 0.1 M HCl is mixed with 50 mL of 0.1 M NaOH, the resulting solution will have:
A pH = 7
B pH < 7
C pH > 7
D pH = 14
Correct Answer:  A. pH = 7
EXPLANATION

Equivalent moles of strong acid and strong base neutralize completely. The salt NaCl formed doesn't hydrolyze. pH = 7

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Q.30 Easy NEET Chemistry Physical Chemistry
The rate constant for a first-order reaction is 0.693 min⁻¹. What is its half-life?
A 0.5 min
B 1 min
C 2 min
D 1.386 min
Correct Answer:  B. 1 min
EXPLANATION

For first-order reaction: t₁/₂ = 0.693/k = 0.693/0.693 = 1 min

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