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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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Topics in JEE Chemistry
The electrochemical series is based on which property?
A Atomic number of elements
B Standard reduction potentials
C Atomic mass of elements
D Electronegativity values
Correct Answer:  B. Standard reduction potentials
EXPLANATION

The electrochemical series arranges elements in order of their standard reduction potentials, with more positive values indicating stronger oxidizing agents.

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What is the effect of temperature on the conductivity of ionic solutions?
A Conductivity decreases with increase in temperature
B Conductivity increases with increase in temperature
C Conductivity remains constant with temperature
D Temperature has no effect on ionic mobility
Correct Answer:  B. Conductivity increases with increase in temperature
EXPLANATION

Conductivity increases with temperature because ionic mobility increases due to decreased viscosity of the medium.

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The standard reduction potential of H⁺/H₂ electrode is taken as 0.00 V because:
A Hydrogen is the most abundant element
B It serves as a reference electrode for all other half-cells
C Hydrogen has zero atomic number
D It's the easiest element to oxidize
Correct Answer:  B. It serves as a reference electrode for all other half-cells
EXPLANATION

SHE (Standard Hydrogen Electrode) is the arbitrary reference against which all other reduction potentials are measured.

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In a Daniel cell, the mass of zinc electrode decreases and copper electrode increases. This indicates:
A Zn acts as anode and Cu as cathode
B Both electrodes are anodes
C Both electrodes are cathodes
D Cu acts as anode and Zn as cathode
Correct Answer:  A. Zn acts as anode and Cu as cathode
EXPLANATION

Anode undergoes oxidation (Zn → Zn²⁺ + 2e⁻), losing mass. Cathode undergoes reduction (Cu²⁺ + 2e⁻ → Cu), gaining mass.

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In the electrolysis of molten NaCl using inert electrodes, what is produced at the cathode?
A Cl₂ gas
B Na metal
C O₂ gas
D NaOH solution
Correct Answer:  B. Na metal
EXPLANATION

At cathode: Na⁺ + e⁻ → Na (reduction). At anode: 2Cl⁻ → Cl₂ + 2e⁻ (oxidation).

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The conductivity of a solution decreased upon dilution. This is because:
A Molar conductivity remains constant
B Number of ions per unit volume decreases
C Degree of ionization increases
D Ionic mobility increases significantly
Correct Answer:  B. Number of ions per unit volume decreases
EXPLANATION

Conductivity (κ) = concentration × molar conductivity. Upon dilution, concentration decreases faster than molar conductivity increases.

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Which electrodes combination gives the maximum EMF in a galvanic cell at 25°C?
A Zn-Cu (E°Zn/Zn²⁺ = -0.76 V, E°Cu/Cu²⁺ = +0.34 V)
B Zn-Ag (E°Zn/Zn²⁺ = -0.76 V, E°Ag/Ag⁺ = +0.80 V)
C Fe-Cu (E°Fe/Fe²⁺ = -0.44 V, E°Cu/Cu²⁺ = +0.34 V)
D Pb-Cu (E°Pb/Pb²⁺ = -0.13 V, E°Cu/Cu²⁺ = +0.34 V)
Correct Answer:  B. Zn-Ag (E°Zn/Zn²⁺ = -0.76 V, E°Ag/Ag⁺ = +0.80 V)
EXPLANATION

Maximum EMF = E°cathode - E°anode = 0.80 - (-0.76) = 1.56 V for Zn-Ag cell.

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In a galvanic cell, if the standard cell potential E°cell is negative, which statement is true?
A The reaction is spontaneous and ΔG° is negative
B The reaction is non-spontaneous and ΔG° is positive
C The cell will not produce any electrical energy
D The cathode potential is greater than anode potential
Correct Answer:  B. The reaction is non-spontaneous and ΔG° is positive
EXPLANATION

Negative E°cell indicates non-spontaneous reaction with positive ΔG°. The relationship is ΔG° = -nFE°cell.

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In the electrochemical series, which metal is most easily oxidized?
A Cu
B Ag
C K
D Au
Correct Answer:  C. K
EXPLANATION

Potassium (K) has the most negative standard reduction potential and is most easily oxidized among the given options. The order of ease of oxidation is K > Cu > Ag > Au.

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The Faraday constant (F) is numerically equal to:
A Avogadro's number × charge of one electron
B Planck's constant × frequency
C Boltzmann constant × temperature
D Gas constant × Avogadro's number
Correct Answer:  A. Avogadro's number × charge of one electron
EXPLANATION

F = N_A × e = 6.022 × 10²³ × 1.602 × 10⁻¹⁹ C = 96485 C/mol, which equals Avogadro's number times the charge of one electron.

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