Free Environmental Chemistry MCQs with Answers

201. Which one is not responsible for the formation of acid rain?

• 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. Carbon monoxide (CO) is not capable of forming an acid when it reacts with water, thus it does not contribute to acid rain. In contrast, carbon dioxide (CO2) can form carbonic acid, sulphur dioxide (SO2) forms sulphuric acid, and nitrogen dioxide (NO2) forms nitric acid, all of which contribute to acid rain. Therefore, CO is the only option that does not lead to acid rain formation.

202. Which has the lowest temperature?

• 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. Hence the correct answer will be C.

203. Rain water becomes acidic, when the pH-value of rain water becomes _

• 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 becomes more acidic has the pH drops below 5.0. Therefore the answer is D.

204. Ozone gas is:

• 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 the answer will be C.

205. The major sources responsible for the presence of NO, N2O, NO2 in the atmosphere is / are:

• 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. This process occurs in vehicles, industrial facilities, and power plants, where high temperatures lead to the formation of nitrogen oxides. Fertilizers and biological decay are lesser sources and primarily contribute to other types of nitrogen emissions, such as ammonia and organic nitrogen compounds, rather than directly to nitrogen oxides.

206. Choose the correct statement:DDT an insecticide is considered as:

• 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 highly stable pesticide with a long environmental half-life, often cited between 2 and 15 years. This persistence is a significant reason for its controversial use and eventual ban in many countries due to environmental and health concerns. The other options underestimate DDT's stability and half-life, making them incorrect.

207. Which statement is correct for three way catalytic converter:

• 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 combustion engines. It does this by using a catalyst to speed up chemical reactions that convert harmful pollutants into less harmful substances. The three main pollutants that a three-way catalytic converter reduces are: Nitrogen oxides (NOx): These are formed when nitrogen and oxygen in the air react at high temperatures. NOx can cause respiratory problems and contribute to smog. Carbon monoxide (CO): This is a colorless, odorless gas that is produced when fuel is not burned completely. CO can reduce the amount of oxygen in the blood, which can lead to headaches, dizziness, and even death. Hydrocarbons (HC): These are compounds that contain hydrogen and carbon. HC can contribute to smog and can also be harmful to human health. A three-way catalytic converter uses a combination of platinum, palladium, and rhodium to speed up the reactions that convert these pollutants into less harmful substances. The catalyst works by providing a surface on which the reactions can occur more easily. The three-way catalytic converter is a very effective way to reduce emissions from internal combustion engines. It can reduce NOx emissions by up to 90%, CO emissions by up to 95%, and HC emissions by up to 99%.

208. Which one of the following is called "black gold"?

• A. Coal tar
• B. Petroleum
• C. Coal
• D. Natural gas

Explanation: It is a black, combustible rock primarily composed of carbon. It is used as a fuel source for power generation and in industrial processes.

209. Ozone layer in upper atmosphere is being destroyed by:

• A. Chlorofluorocarbons
• B. SO2
• C. Smog
• D. Photochemical oxidation

Explanation: The ozone layer in the upper atmosphere is being primarily destroyed by chlorofluorocarbons (CFCs). These are synthetic compounds that release chlorine and bromine atoms when they are broken down in the stratosphere. These released atoms then catalytically destroy ozone molecules, leading to thinning of the ozone layer. Therefore, option a is correct.

210. Super Phosphate is made by:

• A. The acidulation of phosphate rock
• B. The alkylation of phosphate rock
• C. The alcoholation of phosphate rock
• D. The alkali addition of phosphate rock

Explanation: The correct answer is A: "The acidulation of phosphate rock." Superphosphate is a fertilizer that is commonly used to provide plants with phosphorus, an essential nutrient for plant growth. It is made by treating phosphate rock with sulfuric acid in a process known as acidulation. This process converts the insoluble phosphate in the rock into a more soluble form that can be absorbed by plants.