Chemistry

Chemical Reactions and Equations

674 Questions

Chemical reactions and equations form a foundational chemistry topic where students identify reaction products, balance chemical formulas, and classify reaction types. It covers critical mechanisms like Markovnikov's rule, precipitation, and endothermic or exothermic processes. These questions are highly common in general science sections of state and central government competitive exams.

Endothermic reactionsPrecipitation reactionsDehydrohalogenation of alkyl halidesChemical equation balancingReaction product identification

Chemical Reactions and Equations Questions

Multiple choice

Which of the following is not a type of chemical reaction?

  1. Synthesis reaction

  2. Decomposition reaction

  3. Single-replacement reaction

  4. Double-replacement reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Single-replacement reaction is a type of chemical reaction in which one element replaces another element in a compound.

Multiple choice

What is the term for the photochemical reaction in which two molecules combine to form a single molecule?

  1. Photodimerization

  2. Photocycloaddition

  3. Photopolymerization

  4. Photoaddition
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Photocycloaddition is the term for the photochemical reaction in which two molecules combine to form a single molecule, typically involving a [2+2] or [4+2] cycloaddition reaction.

Multiple choice

What is the term for the photochemical reaction in which a molecule undergoes oxidation?

  1. Photooxidation

  2. Photoreduction

  3. Photodissociation

  4. Photoionization
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Photooxidation is the term for the photochemical reaction in which a molecule undergoes oxidation, typically involving the transfer of electrons to an oxidizing agent.

Multiple choice

Which type of chemical reaction is responsible for the formation of complex organic molecules on the surfaces of exoplanets?

  1. Acid-base reactions

  2. Redox reactions

  3. Polymerization reactions

  4. Condensation reactions
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Condensation reactions are responsible for the formation of complex organic molecules on the surfaces of exoplanets by combining smaller molecules into larger ones.

Multiple choice

Which of the following is a green alternative to traditional halogenation reactions?

  1. Electrophilic aromatic substitution

  2. Nucleophilic substitution

  3. Free radical halogenation

  4. Sandmeyer reaction
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Electrophilic aromatic substitution is a green alternative to traditional halogenation reactions because it does not generate hazardous byproducts and allows for regioselectivity in the halogenation of aromatic compounds.

Multiple choice

Which of the following is not a type of chemical reaction?

  1. Synthesis reaction

  2. Decomposition reaction

  3. Single-replacement reaction

  4. Double-replacement reaction

  5. Combustion reaction
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Combustion reactions are not a type of chemical reaction. They are a type of exothermic reaction in which a substance reacts with oxygen to produce heat and light.

Multiple choice

Which of the following is an example of a less hazardous chemical synthesis?

  1. Using water as a solvent instead of organic solvents

  2. Using renewable feedstocks such as plant-based oils instead of fossil fuels

  3. Using catalytic reactions instead of stoichiometric reactions

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Examples of less hazardous chemical syntheses include using water as a solvent instead of organic solvents, which are often toxic and flammable; using renewable feedstocks such as plant-based oils instead of fossil fuels, which are non-renewable and contribute to greenhouse gas emissions; and using catalytic reactions instead of stoichiometric reactions, which generate less waste.

Multiple choice

What is the concept of solvent selection in Less Hazardous Chemical Syntheses?

  1. Choosing a solvent that is non-toxic and environmentally friendly

  2. Choosing a solvent that is inexpensive and readily available

  3. Choosing a solvent that is highly reactive and promotes the desired reaction

  4. Choosing a solvent that is immiscible with the reactants
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Solvent selection is an important aspect of Less Hazardous Chemical Syntheses. The goal is to choose a solvent that is non-toxic, environmentally friendly, and promotes the desired reaction. This may involve using water as a solvent, ionic liquids, or bio-based solvents derived from renewable resources.

Multiple choice

Which of the following is an example of an energy-efficient chemical synthesis?

  1. Using microwave irradiation instead of conventional heating

  2. Using ultrasound instead of mechanical stirring

  3. Using continuous flow reactors instead of batch reactors

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Examples of energy-efficient chemical syntheses include using microwave irradiation instead of conventional heating, which reduces reaction times and energy consumption; using ultrasound instead of mechanical stirring, which improves mixing and reduces energy input; and using continuous flow reactors instead of batch reactors, which enables better control of reaction conditions and reduces energy usage.

Multiple choice

Which of the following is an example of an inherently safe chemical synthesis?

  1. Using a non-flammable solvent instead of a flammable solvent

  2. Using a low-temperature reaction instead of a high-temperature reaction

  3. Using a continuous flow reactor instead of a batch reactor

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Examples of inherently safe chemical syntheses include using a non-flammable solvent instead of a flammable solvent, which reduces the risk of fire; using a low-temperature reaction instead of a high-temperature reaction, which reduces the risk of explosions; and using a continuous flow reactor instead of a batch reactor, which provides better control of reaction conditions and reduces the risk of runaway reactions.

Multiple choice

The overall reaction for gasification of coal is:

  1. C + H₂O → CO + H₂

  2. C + 2H₂O → CO₂ + 2H₂

  3. C + 3H₂O → CO₂ + 3H₂

  4. C + 4H₂O → CO₂ + 4H₂
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The overall reaction for gasification of coal is C + H₂O → CO + H₂.

Multiple choice

The overall reaction for electrolysis of water is:

  1. 2H₂O → 2H₂ + O₂

  2. 2H₂O → H₂ + 2O₂

  3. 2H₂O → 3H₂ + O₂

  4. 2H₂O → 4H₂ + O₂
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The overall reaction for electrolysis of water is 2H₂O → 2H₂ + O₂.

Multiple choice

Which of the following is an example of a radical-radical reaction commonly observed in astrochemical environments?

  1. H + OH → H2O

  2. CH3 + CH3 → C2H6

  3. O + H2 → OH + H

  4. CO + O → CO2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

CH3 + CH3 → C2H6 is an example of a radical-radical reaction, where two methyl radicals combine to form ethane (C2H6).

Multiple choice

Which of the following is an example of a photodissociation reaction commonly observed in astrochemical environments?

  1. CO2 + hv → CO + O

  2. H2O + hv → H + OH

  3. CH4 + hv → CH3 + H

  4. NH3 + hv → NH2 + H
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

CO2 + hv → CO + O is an example of a photodissociation reaction, where carbon dioxide (CO2) absorbs a photon of light and breaks apart into carbon monoxide (CO) and oxygen (O).

Multiple choice

What is the name of the reaction in which nitrites are oxidized to nitrates?

  1. Nitrification

  2. Denitrification

  3. Assimilation

  4. Mineralization
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The reaction in which nitrites are oxidized to nitrates is called nitrification.