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JEE Main MCQ questions — Mathematics, Physics, Chemistry for engineering entrance.

158 Q 3 Subjects 12th (PCM)
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Q.131 Easy JEE Chemistry Physical Chemistry
Which of the following best explains why diamond is harder than graphite?
A Stronger hydrogen bonding in diamond
B Three-dimensional covalent network structure in diamond
C Diamond has more carbon atoms per unit volume
D Presence of metallic bonding in diamond
Correct Answer:  B. Three-dimensional covalent network structure in diamond
EXPLANATION

Diamond has a 3D tetrahedral covalent network structure with C-C bonds in all directions, while graphite has layered structure with weak van der Waals forces between layers

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Q.132 Easy JEE Chemistry Physical Chemistry
For electrodeposition of copper using 1 Faraday of charge, how many moles of Cu are deposited? Cu²⁺ + 2e⁻ → Cu
A 1 mol
B 0.5 mol
C 2 mol
D 0.25 mol
Correct Answer:  B. 0.5 mol
EXPLANATION

Cu²⁺ requires 2 electrons per atom. 1 Faraday = 1 mol of electrons; moles of Cu = 1/2 = 0.5 mol

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Q.133 Easy JEE Chemistry Physical Chemistry
Which of the following has maximum boiling point?
A H₂O
B H₂S
C H₂Se
D H₂Te
Correct Answer:  A. H₂O
EXPLANATION

H₂O has maximum boiling point due to strong hydrogen bonding compared to other hydrides in group 16

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Q.134 Easy JEE Chemistry Physical Chemistry
Which factor does NOT affect the rate of a chemical reaction?
A Temperature
B Catalyst
C Color of reactants
D Concentration of reactants
Correct Answer:  C. Color of reactants
EXPLANATION

Color of reactants has no effect on reaction rate. Temperature, catalyst, and concentration all significantly affect reaction rate.

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Q.135 Easy JEE Chemistry Physical Chemistry
The standard reduction potential for Zn²⁺/Zn is -0.76 V and for Cu²⁺/Cu is +0.34 V. Calculate E°cell for Zn-Cu galvanic cell.
A 1.10 V
B 1.00 V
C 0.42 V
D 0.58 V
Correct Answer:  A. 1.10 V
EXPLANATION

E°cell = E°cathode - E°anode = 0.34 - (-0.76) = 1.10 V

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Q.136 Easy JEE Chemistry Physical Chemistry
A solution has [H⁺] = 1 × 10⁻⁷ M and [OH⁻] = 1 × 10⁻⁷ M at 25°C. Which statement is true?
A The solution is acidic
B The solution is basic
C The solution is neutral
D The solution is a buffer
Correct Answer:  C. The solution is neutral
EXPLANATION

[H⁺] = [OH⁻] indicates a neutral solution. At 25°C, Kw = [H⁺][OH⁻] = 1 × 10⁻¹⁴, so pH = 7, pOH = 7 confirms neutrality.

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Q.137 Easy JEE Chemistry Physical Chemistry
Which electrode reaction occurs at the anode in a galvanic cell?
A Reduction
B Oxidation
C Hydrolysis
D Dehydration
Correct Answer:  B. Oxidation
EXPLANATION

In a galvanic cell, anode is where oxidation occurs (loss of electrons). The cathode is where reduction occurs (gain of electrons).

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Q.138 Easy JEE Chemistry Physical Chemistry
For a galvanic cell: Cu²⁺ + 2e⁻ → Cu (E° = 0.34 V) and Zn²⁺ + 2e⁻ → Zn (E° = -0.76 V). What is the standard cell potential (E°cell)?
A 1.10 V
B 0.42 V
C -1.10 V
D 1.56 V
Correct Answer:  A. 1.10 V
EXPLANATION

E°cell = E°cathode - E°anode = 0.34 - (-0.76) = 1.10 V. Cu is cathode (reduction), Zn is anode (oxidation).

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Q.139 Easy JEE Chemistry Physical Chemistry
For the complex ion [Cu(NH₃)₄]²⁺, what is the coordination number of Cu²⁺?
A 2
B 4
C 6
D 8
Correct Answer:  B. 4
EXPLANATION

The coordination number is the number of ligands attached to the central metal ion. Here, 4 NH₃ ligands are bonded to Cu²⁺, so coordination number = 4.

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Q.140 Easy JEE Chemistry Physical Chemistry
For the reaction 2A + B → C, if the rate law is Rate = k[A]²[B], what is the overall order of the reaction?
A 1
B 2
C 3
D 4
Correct Answer:  C. 3
EXPLANATION

Overall order = sum of exponents in rate law = 2 + 1 = 3 (third-order reaction). Note: order is determined experimentally, not from stoichiometry.

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