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JEE Chemistry

Chemistry questions for JEE Main — Physical, Organic, Inorganic Chemistry.

143 Q 5 Topics Take Test
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Difficulty: All Easy Medium Hard 51–60 of 143
Topics in JEE Chemistry
Which element shows variable oxidation states primarily due to incomplete d-orbitals?
A Zinc
B Copper
C Manganese
D Calcium
Correct Answer:  C. Manganese
EXPLANATION

Transition metals like Mn show multiple oxidation states (+2, +3, +4, +6, +7) due to incomplete d-orbitals. Zn shows only +2, Cu shows +1 and +2.

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The oxidation state of bromine in KBrO₄ is:
A +5
B +7
C +3
D +6
Correct Answer:  B. +7
EXPLANATION

In KBrO₄, K is +1 and each O is -2. Therefore: 1 + x + 4(-2) = 0, giving x = +7. Bromine achieves its maximum oxidation state in this perbromate ion.

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In the contact process for H₂SO₄ manufacture, the catalyst used is:
A Iron
B Vanadium pentoxide
C Platinum
D Copper oxide
Correct Answer:  B. Vanadium pentoxide
EXPLANATION

V₂O₅ is the standard catalyst used in the oxidation of SO₂ to SO₃. It provides excellent activity and selectivity at 400-450°C operational temperature.

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The aqueous solution of which salt is most acidic due to hydrolysis?
A NaCl
B FeCl₃
C NH₄Cl
D Na₂CO₃
Correct Answer:  B. FeCl₃
EXPLANATION

FeCl₃ undergoes significant hydrolysis: Fe³⁺ + H₂O ⇌ Fe(OH)²⁺ + H⁺. Fe³⁺ is a strong Lewis acid causing extensive hydrolysis and acidic solution.

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The hybridization of sulphur in SF₆ molecule is:
A sp³
B sp³d
C sp³d²
D d²sp³
Correct Answer:  C. sp³d²
EXPLANATION

SF₆ has 6 fluorine atoms bonded to sulphur with octahedral geometry. The hybridization is sp³d² involving d-orbitals from the third shell.

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In the extraction of iron from haematite using blast furnace, the reducing agent is primarily:
A Carbon monoxide
B Carbon dioxide
C Coke
D Limestone
Correct Answer:  A. Carbon monoxide
EXPLANATION

CO produced in the blast furnace acts as the primary reducing agent for Fe₂O₃. Although coke is fed, CO generated from coke combustion performs the actual reduction.

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The coordination number of Co in [Co(NH₃)₆]³⁺ complex is:
A 3
B 4
C 6
D 8
Correct Answer:  C. 6
EXPLANATION

Coordination number is the number of ligands bonded to the central metal. Six NH₃ molecules surround Co³⁺, giving coordination number 6.

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Which of the following noble gases has the lowest ionization energy?
A Helium
B Neon
C Argon
D Xenon
Correct Answer:  D. Xenon
EXPLANATION

Ionization energy decreases down a group. Xenon (54 electrons) has the largest atomic radius and lowest ionization energy among noble gases listed.

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The primary use of zinc in brass alloy is to:
A Increase hardness
B Decrease ductility
C Provide corrosion resistance and workability
D Act as a catalyst
Correct Answer:  C. Provide corrosion resistance and workability
EXPLANATION

Zinc in brass (Cu-Zn alloy) enhances corrosion resistance through protective layer formation and improves cold-workability of copper.

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The standard electrode potential for Zn²⁺/Zn is -0.76 V. In a galvanic cell combining Zn and Cu electrodes, Zn will act as:
A Cathode (positive electrode)
B Anode (negative electrode)
C Both cathode and anode alternately
D Neither cathode nor anode
Correct Answer:  B. Anode (negative electrode)
EXPLANATION

Zn has lower (more negative) reduction potential than Cu, making it more easily oxidized. It acts as the anode (negative electrode) in the galvanic cell.

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