All Free Chemistry MCQs with Answers

• A. Br2 in organic solvent
• B. Baeyer's reagent
• C. Phenyl Hydrazine
• D. Tollen's reagent

Explanation: The correct answer is Tollen's reagent. Ethene does not react with Tollen's reagent, whereas Ethyne reacts with it to form a white…

• A. CnH2n+2
• B. CnH2n
• C. CnH2n-2
• D. Both CnH2n and CnH2n-2

Explanation: Alkynes on hydration in the presence of H2SO4 and HgSO4 yield carbonyl compounds through enolAll alkynes except ethyne give ketones while…

• A. Toluene
• B. 2-butyne
• C. 1-butyne
• D. 2-butene

Explanation: EToluene, which is a hydrocarbon, does not typically undergo acid-base reactions.

• A. Vinyl chloride
• B. Ethyl chloride
• C. 1,2 - dichloroethane
• D. 1,1 - dichloroethane

Explanation: When excess hydrochloric acid (HCl) is added to acetylene (C2H2), the product formed is 1,2 - dichloroethane (C2H4Cl2).

• A. Colorless
• B. Is a bad conductor
• C. Does not expand linearly
• D. Has a low boiling point of 100oC

Explanation: The correct answer is that water does not expand linearly. Water's anomalous expansion, particularly its contraction from 0°C to 4°C and…

• A. Lighter
• B. Highest
• C. Heavier
• D. Heaviest

Explanation: Water has the highest density at 4 degree C as the cage-like structure which forms when water freezes starts breaking.

• A. Methane
• B. CO2
• C. Nitrous oxide
• D. Sulphur dioxide

Explanation: The greenhouse effect is how heat is trapped close to Earth's surface by "greenhouse gases." Greenhouse gases include CO2, methane, and…

• A. Acid rain
• B. Green house effect
• C. Global warming
• D. Ozone depletion

Explanation: Acid rain: SO2 is a major contributor to the formation of acid rain. When released into the atmosphere, it reacts with water and other…

• A. Air pollution
• B. Water pollution
• C. Acid rain
• D. Ozone layer depletion

Explanation: Chlorofluorocarbons (CFCs) are mainly responsible for ozone layer depletion.

• A. burning of coal
• B. burning of charcoal
• C. automobile engines
• D. refrigeration and air conditioning

Explanation: Chloroflorocarbons are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine.

• A. CO2
• B. CO
• C. Low hydrocarbons
• D. All of them

Explanation: CO2 is the major vehicular emission responsible for causing the greenhouse effect and environmental pollution.

• A. CO2
• B. CO
• C. Lead
• D. Free radica ethyne (C2H2)

Explanation: TEL can cause chronic lead poisoning, and hence its hazardous product is lead.

• A. CO2
• B. SO2
• C. CH4
• D. NO2

Explanation: When paper biodegrades, especially in the presence of oxygen, the primary gas emitted is carbon dioxide (CO2), due to the aerobic…

• A. CO2
• B. SO2
• C. CO
• D. NO2

Explanation: Acid rain is primarily caused by the dissolution of specific oxides in atmospheric moisture, leading to acidic compounds.

• A. Troposphere
• B. Stratosphere
• C. Mesosphere
• D. Thermosphere

Explanation: The top of the mesosphere, called the mesopause is the coldest part of the earth's atmosphere averaging about minus 130 degrees F.

• A. Greater than 6
• B. Greater than 6.5
• C. Less than 5.6
• D. Less than 5

Explanation: Normal clean rain has a pH value between 5.0 - 5.5, which is slightly acidic, however when rain combines with nitrogen oxides or SO2, it…

• A. Greenish, tasteless and light
• B. Greenish blue, bitter in taste
• C. Blue. Poisonous and explosive
• D. Purple yellow, non poisonous, non explosive

Explanation: Ozone gas is pale blue,it is a toxic substance and can lead to explosive destruction when concentrated and a trigger is applied, therefore…

• A. Fertilizers
• B. Biological decay of organic matter
• C. Fossil fuel combustion
• D. All of these

Explanation: Fossil fuel combustion is the major source of NO, NO2, and N2O in the atmosphere.

• A. Very unstable molecule having a half-life of 1⁄2 to 1 year
• B. Unstable molecule having a half-life of 2 to 5 years
• C. Stable molecule having a half-life of 5 to 8 years
• D. Very stable molecule having a half-life of 10 to 15 years

Explanation: The correct answer is Option D: 'Very stable molecule having a half-life of 10 to 15 years.' DDT (Dichlorodiphenyltrichloroethane) is a…

• A. Reduces emission of unburnt HC's
• B. Reduces pollutants
• C. Oxidize pollutant like CO
• D. All of the above

Explanation: The correct statement is ALL OF THE ABOVE. A three-way catalytic converter is a device that is used to reduce emissions from internal…