Chemistry (School & UG)
Q. What is the mechanism of the nitration of benzene?
A.
Electrophilic addition
B.
Nucleophilic substitution
C.
Electrophilic substitution
D.
Radical substitution
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Solution
The mechanism of nitration of benzene is electrophilic substitution, where the nitronium ion acts as the electrophile.
Correct Answer: C — Electrophilic substitution
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Q. What is the mechanism of the reaction between 1-bromobutane and sodium hydroxide in ethanol?
A.
SN1
B.
SN2
C.
E1
D.
E2
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Solution
The reaction proceeds via an SN2 mechanism due to the primary nature of 1-bromobutane, allowing for a backside attack by the nucleophile.
Correct Answer: B — SN2
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Q. What is the mechanism of the reaction between an alkyl halide and a nucleophile in a bimolecular nucleophilic substitution (SN2)?
A.
Nucleophile attacks from the back side, leading to inversion of configuration
B.
Nucleophile attacks from the front side, leading to retention of configuration
C.
Formation of a carbocation intermediate
D.
Nucleophile attacks the halogen first
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Solution
In an SN2 reaction, the nucleophile attacks the carbon from the opposite side of the leaving group, resulting in inversion of configuration.
Correct Answer: A — Nucleophile attacks from the back side, leading to inversion of configuration
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Q. What is the mechanism of the reaction between an alkyl halide and a nucleophile in a bimolecular nucleophilic substitution (SN2) reaction?
A.
The nucleophile attacks the carbon from the opposite side of the leaving group.
B.
The nucleophile attacks the carbon from the same side as the leaving group.
C.
The reaction proceeds through a carbocation intermediate.
D.
The reaction involves the formation of a cyclic intermediate.
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Solution
In an SN2 reaction, the nucleophile attacks the carbon atom from the opposite side of the leaving group, leading to a backside attack and inversion of configuration.
Correct Answer: A — The nucleophile attacks the carbon from the opposite side of the leaving group.
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Q. What is the mechanism of the reaction of 2-bromobutane with potassium cyanide?
A.
SN1
B.
SN2
C.
E1
D.
E2
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Solution
The reaction proceeds via an SN2 mechanism, as 2-bromobutane is a secondary haloalkane and the nucleophile attacks from the opposite side.
Correct Answer: B — SN2
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Q. What is the molarity of a sodium hydroxide solution if 0.4 moles are dissolved in 2 liters of water?
A.
0.2 M
B.
0.4 M
C.
0.5 M
D.
0.8 M
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Solution
Molarity (M) = moles of solute / liters of solution. Here, M = 0.4 moles / 2 L = 0.2 M.
Correct Answer: B — 0.4 M
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Q. What is the molecular formula for 2,3-dimethylpentane?
A.
C7H16
B.
C8H18
C.
C6H14
D.
C5H12
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Solution
2,3-dimethylpentane has a total of 7 carbons and 16 hydrogens, giving it the molecular formula C7H16.
Correct Answer: A — C7H16
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Q. What is the molecular formula for 2-butyne?
A.
C4H8
B.
C4H6
C.
C4H10
D.
C4H12
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Solution
2-butyne is an alkyne with the formula C4H6, as it contains a triple bond.
Correct Answer: B — C4H6
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Q. What is the molecular formula for 3-methyl-1-butyne?
A.
C5H10
B.
C5H8
C.
C6H10
D.
C6H12
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Solution
3-methyl-1-butyne has the molecular formula C5H8, as it contains a triple bond.
Correct Answer: B — C5H8
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Q. What is the molecular formula of 2,3-dimethylbutane?
A.
C7H16
B.
C6H14
C.
C8H18
D.
C5H12
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Solution
2,3-dimethylbutane has a total of 7 carbon atoms and 16 hydrogen atoms, giving the formula C7H16.
Correct Answer: A — C7H16
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Q. What is the molecular formula of 2-butyne?
A.
C4H6
B.
C4H8
C.
C4H10
D.
C4H4
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Solution
2-butyne has a triple bond and contains 4 carbons and 6 hydrogens, giving the formula C4H6.
Correct Answer: A — C4H6
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Q. What is the molecular formula of the compound formed when hydrogen reacts with chlorine?
A.
HCl
B.
H2Cl2
C.
Cl2H2
D.
H3Cl
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Solution
The molecular formula of the compound formed when hydrogen reacts with chlorine is HCl (hydrochloric acid).
Correct Answer: A — HCl
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Q. What is the molecular geometry of a molecule with 2 bonding pairs and 2 lone pairs on the central atom?
A.
Linear
B.
Trigonal Planar
C.
Tetrahedral
D.
Bent
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Solution
With 2 bonding pairs and 2 lone pairs, the molecular geometry is bent due to the repulsion of lone pairs.
Correct Answer: D — Bent
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Q. What is the molecular geometry of a molecule with a trigonal bipyramidal electron geometry and one lone pair?
A.
T-shaped
B.
Linear
C.
Trigonal planar
D.
Octahedral
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Solution
A trigonal bipyramidal electron geometry with one lone pair results in a T-shaped molecular geometry.
Correct Answer: A — T-shaped
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Q. What is the molecular geometry of CO2?
A.
Linear
B.
Bent
C.
Trigonal Planar
D.
Tetrahedral
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Solution
CO2 has a linear geometry due to the arrangement of two double bonds around the central carbon atom.
Correct Answer: A — Linear
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Q. What is the molecular geometry of NH3?
A.
Linear
B.
Trigonal planar
C.
Tetrahedral
D.
Trigonal pyramidal
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Solution
NH3 has three bonding pairs and one lone pair, resulting in a trigonal pyramidal geometry.
Correct Answer: D — Trigonal pyramidal
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Q. What is the molecular geometry of PCl5?
A.
Trigonal planar
B.
Tetrahedral
C.
Octahedral
D.
Trigonal bipyramidal
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Solution
PCl5 has 5 bonding pairs and no lone pairs, resulting in a trigonal bipyramidal geometry.
Correct Answer: D — Trigonal bipyramidal
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Q. What is the molecular geometry of SF6?
A.
Octahedral
B.
Tetrahedral
C.
Trigonal bipyramidal
D.
Square planar
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Solution
SF6 has an octahedral geometry due to six bonding pairs of electrons around the central sulfur atom, with bond angles of 90 degrees.
Correct Answer: A — Octahedral
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Q. What is the molecular geometry of sulfur hexafluoride (SF6)?
A.
Octahedral
B.
Tetrahedral
C.
Trigonal bipyramidal
D.
Square planar
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Solution
SF6 has six bonding pairs and no lone pairs, resulting in an octahedral molecular geometry.
Correct Answer: A — Octahedral
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Q. What is the molecular geometry of the sulfate ion (SO4^2-)?
A.
Linear
B.
Trigonal planar
C.
Tetrahedral
D.
Octahedral
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Solution
The sulfate ion has four bonding pairs and no lone pairs, resulting in a tetrahedral molecular geometry.
Correct Answer: C — Tetrahedral
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Q. What is the Nernst equation for a half-reaction involving 2 electrons at 25°C?
A.
E = E° - 0.059/n log(Q)
B.
E = E° + 0.059/n log(Q)
C.
E = E° - 0.0257/n log(Q)
D.
E = E° + 0.0257/n log(Q)
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Solution
The Nernst equation is E = E° - (0.059/n)log(Q) at 25°C.
Correct Answer: A — E = E° - 0.059/n log(Q)
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Q. What is the Nernst equation used for calculating the cell potential under non-standard conditions?
A.
E = E° - (RT/nF)ln(Q)
B.
E = E° + (RT/nF)ln(Q)
C.
E = E° - (nF/RT)ln(Q)
D.
E = E° + (nF/RT)ln(Q)
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Solution
The Nernst equation is E = E° - (RT/nF)ln(Q), where R is the gas constant, T is temperature, n is moles of electrons, and F is Faraday's constant.
Correct Answer: A — E = E° - (RT/nF)ln(Q)
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Q. What is the Nernst equation used for in electrochemistry?
A.
Calculating cell potential
B.
Determining reaction rate
C.
Measuring pH
D.
Assessing temperature changes
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Solution
The Nernst equation relates the cell potential to the concentrations of reactants and products, allowing for the calculation of cell voltage under non-standard conditions.
Correct Answer: A — Calculating cell potential
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Q. What is the net ionic equation for the reaction between H2SO4 and NaOH?
A.
H+ + OH- -> H2O
B.
Na+ + SO4^2- -> Na2SO4
C.
H2SO4 + NaOH -> Na2SO4 + H2O
D.
H2O -> H+ + OH-
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Solution
The net ionic equation shows the formation of water from hydrogen ions and hydroxide ions.
Correct Answer: A — H+ + OH- -> H2O
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Q. What is the order of a reaction if the rate law is given by rate = k[A]^2[B]?
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Solution
The order of the reaction is the sum of the exponents in the rate law. Here, it is 2 (from [A]^2) + 1 (from [B]) = 3.
Correct Answer: C — 2
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Q. What is the oxidation state of chromium in potassium dichromate (K2Cr2O7)?
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Solution
In potassium dichromate, chromium has an oxidation state of +6.
Correct Answer: C — +6
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Q. What is the oxidation state of chromium in the complex ion [Cr(NH3)6]Cl3?
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Solution
In the complex [Cr(NH3)6]Cl3, the ammonia ligands are neutral, so the oxidation state of chromium is +3.
Correct Answer: B — +3
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Q. What is the oxidation state of chromium in the complex [Cr(NH3)4Cl2]+?
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Solution
The oxidation state of chromium is +3, calculated from the charges of the ligands.
Correct Answer: B — +3
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Q. What is the oxidation state of chromium in the complex [Cr(NH3)6]Cl3?
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Solution
In [Cr(NH3)6]Cl3, the ammonia ligands are neutral, so the oxidation state of chromium is +3.
Correct Answer: B — +3
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Q. What is the oxidation state of hydrogen in HCl?
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Solution
In HCl, hydrogen has an oxidation state of +1.
Correct Answer: C — +1
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