Major Competitive Exams
Q. Which of the following quantum numbers is not associated with the electron spin?
Show solution
Solution
The principal quantum number n is not associated with electron spin; it describes the energy level.
Correct Answer: A — n
Learn More →
Q. Which of the following quantum numbers is not associated with the electron's energy level?
Show solution
Solution
The spin quantum number (m_s) does not affect the energy level of the electron.
Correct Answer: D — m_s
Learn More →
Q. Which of the following quantum numbers is not associated with the spin of an electron?
Show solution
Solution
The principal quantum number n, azimuthal quantum number l, and magnetic quantum number m_l do not describe the spin of an electron. The spin quantum number s does.
Correct Answer: A — n
Learn More →
Q. Which of the following reactions can alkynes undergo?
A.
Electrophilic addition
B.
Nucleophilic substitution
C.
Free radical substitution
D.
All of the above
Show solution
Solution
Alkynes can undergo electrophilic addition reactions due to the presence of the triple bond.
Correct Answer: A — Electrophilic addition
Learn More →
Q. Which of the following reactions can be used to convert an alkene into an alcohol?
A.
Hydrogenation
B.
Hydroboration-oxidation
C.
Dehydrohalogenation
D.
Electrophilic addition
Show solution
Solution
Hydroboration-oxidation is a two-step process that converts alkenes into alcohols.
Correct Answer: B — Hydroboration-oxidation
Learn More →
Q. Which of the following reactions can be used to convert an alkyne to a cis-alkene?
A.
Hydrogenation
B.
Halogenation
C.
Hydroboration
D.
Ozonolysis
Show solution
Solution
Hydroboration followed by oxidation converts alkynes to cis-alkenes.
Correct Answer: C — Hydroboration
Learn More →
Q. Which of the following reactions can be used to convert an alkyne to an alkene?
A.
Hydrogenation
B.
Halogenation
C.
Hydrohalogenation
D.
Dehydrohalogenation
Show solution
Solution
Hydrogenation of an alkyne will add hydrogen across the triple bond, converting it to an alkene.
Correct Answer: A — Hydrogenation
Learn More →
Q. Which of the following reactions can be used to prepare alkynes?
A.
Hydrogenation of alkenes
B.
Dehydrohalogenation of alkyl halides
C.
Oxidation of alkanes
D.
Hydrolysis of alkynes
Show solution
Solution
Alkynes can be prepared by the dehydrohalogenation of alkyl halides.
Correct Answer: B — Dehydrohalogenation of alkyl halides
Learn More →
Q. Which of the following reactions can be used to prepare carboxylic acids?
A.
Hydrolysis of esters
B.
Reduction of ketones
C.
Oxidation of alcohols
D.
All of the above
Show solution
Solution
Carboxylic acids can be prepared by the hydrolysis of esters.
Correct Answer: A — Hydrolysis of esters
Learn More →
Q. Which of the following reactions has a negative enthalpy change?
A.
Dissolving NaCl in water
B.
Photosynthesis
C.
Respiration
D.
Melting of ice
Show solution
Solution
Respiration is an exothermic reaction that releases energy, resulting in a negative enthalpy change.
Correct Answer: C — Respiration
Learn More →
Q. Which of the following reactions has a positive ΔG at standard conditions?
A.
Combustion of glucose
B.
Formation of water from hydrogen and oxygen
C.
Dissolution of salt in water
D.
Decomposition of hydrogen peroxide
Show solution
Solution
The decomposition of hydrogen peroxide is non-spontaneous under standard conditions, resulting in a positive ΔG.
Correct Answer: D — Decomposition of hydrogen peroxide
Learn More →
Q. Which of the following reactions has a positive ΔH and a positive ΔS?
A.
Combustion of fuels
B.
Dissolution of salts
C.
Sublimation of dry ice
D.
Formation of water from hydrogen and oxygen
Show solution
Solution
Sublimation of dry ice (solid CO2 to gas) has a positive ΔH (endothermic) and a positive ΔS (increase in disorder).
Correct Answer: C — Sublimation of dry ice
Learn More →
Q. Which of the following reactions has the highest enthalpy change?
A.
Dissolving NaCl in water
B.
Combustion of propane
C.
Formation of NH3 from N2 and H2
D.
Sublimation of dry ice
Show solution
Solution
The combustion of propane releases a large amount of energy, resulting in the highest enthalpy change among the options.
Correct Answer: B — Combustion of propane
Learn More →
Q. Which of the following reactions involves a redox process? (2019)
A.
H2 + Cl2 → 2HCl
B.
NaCl → Na + Cl2
C.
CaCO3 → CaO + CO2
D.
H2O → H2 + O2
Show solution
Solution
H2O → H2 + O2 involves the oxidation of water to hydrogen and oxygen, making it a redox reaction.
Correct Answer: D — H2O → H2 + O2
Learn More →
Q. Which of the following reactions is a redox reaction?
A.
H2 + Cl2 → 2HCl
B.
NaOH + HCl → NaCl + H2O
C.
CaCO3 → CaO + CO2
D.
C6H12O6 + 6O2 → 6CO2 + 6H2O
Show solution
Solution
The combustion of glucose is a redox reaction where glucose is oxidized.
Correct Answer: D — C6H12O6 + 6O2 → 6CO2 + 6H2O
Learn More →
Q. Which of the following reactions is a reduction? (2020)
A.
Fe2O3 + 3CO → 2Fe + 3CO2
B.
2H2 + O2 → 2H2O
C.
2Na + Cl2 → 2NaCl
D.
C + O2 → CO2
Show solution
Solution
In the reaction Fe2O3 + 3CO → 2Fe + 3CO2, iron (Fe) is reduced as it gains electrons from carbon monoxide (CO).
Correct Answer: A — Fe2O3 + 3CO → 2Fe + 3CO2
Learn More →
Q. Which of the following reactions is an example of a redox reaction? (2023)
A.
H2 + Cl2 → 2HCl
B.
NaOH + HCl → NaCl + H2O
C.
CaCO3 → CaO + CO2
D.
C + O2 → CO2
Show solution
Solution
The reaction C + O2 → CO2 is a redox reaction because carbon is oxidized and oxygen is reduced.
Correct Answer: D — C + O2 → CO2
Learn More →
Q. Which of the following reactions is an example of hydrogenation? (2023)
A.
Addition of H2 to ethene
B.
Decomposition of water
C.
Formation of ammonia from nitrogen and hydrogen
D.
Combustion of hydrogen
Show solution
Solution
Hydrogenation refers to the addition of hydrogen (H2) to unsaturated hydrocarbons, such as the addition to ethene to form ethane.
Correct Answer: A — Addition of H2 to ethene
Learn More →
Q. Which of the following reactions is characteristic of aldehydes? (2023)
A.
Oxidation to carboxylic acids
B.
Reduction to alcohols
C.
Condensation with alcohols
D.
All of the above
Show solution
Solution
Aldehydes can undergo oxidation to form carboxylic acids, reduction to form alcohols, and condensation with alcohols to form hemiacetals.
Correct Answer: D — All of the above
Learn More →
Q. Which of the following reactions is characteristic of alkanes?
A.
Electrophilic substitution
B.
Nucleophilic substitution
C.
Free radical substitution
D.
Addition reaction
Show solution
Solution
Alkanes undergo free radical substitution reactions, especially in the presence of halogens.
Correct Answer: C — Free radical substitution
Learn More →
Q. Which of the following reactions is characteristic of alkenes?
A.
Electrophilic addition
B.
Nucleophilic substitution
C.
Free radical substitution
D.
Elimination
Show solution
Solution
Alkenes undergo electrophilic addition reactions due to the presence of a double bond.
Correct Answer: A — Electrophilic addition
Learn More →
Q. Which of the following reactions is characteristic of aromatic compounds?
A.
Addition reaction
B.
Substitution reaction
C.
Elimination reaction
D.
Redox reaction
Show solution
Solution
Aromatic compounds typically undergo electrophilic substitution reactions rather than addition reactions due to their stable aromaticity.
Correct Answer: B — Substitution reaction
Learn More →
Q. Which of the following reactions is expected to have a positive change in entropy?
A.
N2(g) + 3H2(g) → 2NH3(g)
B.
C(s) + O2(g) → CO2(g)
C.
2H2O(l) → 2H2(g) + O2(g)
D.
CaCO3(s) → CaO(s) + CO2(g)
Show solution
Solution
The decomposition of liquid water into gaseous hydrogen and oxygen increases the number of gas molecules, leading to a positive change in entropy.
Correct Answer: C — 2H2O(l) → 2H2(g) + O2(g)
Learn More →
Q. Which of the following reactions is likely to have a negative ΔG?
A.
Combustion of hydrocarbons.
B.
Formation of ice from water at 0°C.
C.
Dissolution of salt in water.
D.
Decomposition of hydrogen peroxide.
Show solution
Solution
The combustion of hydrocarbons is highly exothermic and typically has a negative ΔG, indicating spontaneity.
Correct Answer: A — Combustion of hydrocarbons.
Learn More →
Q. Which of the following reactions is not typical for alkenes?
A.
Addition of H2
B.
Addition of HCl
C.
Elimination of H2O
D.
Substitution reaction
Show solution
Solution
Alkenes typically undergo addition reactions rather than substitution reactions.
Correct Answer: D — Substitution reaction
Learn More →
Q. Which of the following reactions is spontaneous at all temperatures?
A.
ΔH < 0 and ΔS < 0
B.
ΔH > 0 and ΔS > 0
C.
ΔH < 0 and ΔS > 0
D.
ΔH > 0 and ΔS < 0
Show solution
Solution
A reaction with ΔH < 0 and ΔS > 0 is spontaneous at all temperatures because it results in a negative ΔG.
Correct Answer: C — ΔH < 0 and ΔS > 0
Learn More →
Q. Which of the following reactions will have a negative ΔG at high temperatures?
A.
Exothermic reactions with negative ΔS
B.
Endothermic reactions with positive ΔS
C.
Exothermic reactions with positive ΔS
D.
Endothermic reactions with negative ΔS
Show solution
Solution
Endothermic reactions with positive ΔS can have a negative ΔG at high temperatures due to the TΔS term becoming significant.
Correct Answer: B — Endothermic reactions with positive ΔS
Learn More →
Q. Which of the following regions is known for its unique biodiversity and is often referred to as a 'biodiversity hotspot'?
A.
Amazon Rainforest
B.
Sahara Desert
C.
Himalayan Region
D.
Great Plains
Show solution
Solution
The Amazon Rainforest is recognized as a biodiversity hotspot due to its vast array of plant and animal species, many of which are endemic to the region.
Correct Answer: A — Amazon Rainforest
Learn More →
Q. Which of the following relations is an equivalence relation on the set of integers?
A.
x ~ y if x + y is even
B.
x ~ y if x - y is prime
C.
x ~ y if x > y
D.
x ~ y if x = y
Show solution
Solution
The relation x ~ y if x + y is even is reflexive, symmetric, and transitive, thus it is an equivalence relation.
Correct Answer: A — x ~ y if x + y is even
Learn More →
Q. Which of the following relations is not a function?
A.
R = {(1, 2), (2, 3), (3, 4)}
B.
R = {(1, 2), (1, 3)}
C.
R = {(2, 3), (3, 4)}
D.
R = {(4, 5), (5, 6)}
Show solution
Solution
R = {(1, 2), (1, 3)} is not a function because the input 1 maps to two different outputs.
Correct Answer: B — R = {(1, 2), (1, 3)}
Learn More →
Showing 17641 to 17670 of 18756 (626 Pages)