Environmental Chemistry Practice Questions

Correct answer: Carbon dioxide

Carbon dioxide is the greenhouse gas most responsible for the enhanced greenhouse effect, because it absorbs outgoing infrared radiation and re-emits it towards the surface. Nitrogen and oxygen make up the bulk of the atmosphere but do not absorb infrared, and carbon monoxide affects the climate only indirectly.

Correct answer: Chlorofluorocarbons

Chlorofluorocarbons release chlorine atoms when ultraviolet radiation breaks them apart in the stratosphere. Each chlorine atom then acts as a catalyst that converts many ozone molecules into ordinary oxygen, thinning the protective layer.

Correct answer: Nitric acid and Sulfuric acid

Sulfur dioxide and nitrogen oxides released by burning fossil fuels react with water vapour and oxygen in the atmosphere to form sulfuric acid and nitric acid. These fall as precipitation and lower the pH of soils and water bodies.

Correct answer: Biological Oxygen Demand

BOD (Biochemical/Biological Oxygen Demand) measures the amount of dissolved oxygen needed by aerobic biological organisms to break down organic material in water. High BOD levels indicate significant organic pollution.

Correct answer: Nitrates

High nitrate levels in drinking water can be converted to nitrites in the body, which interfere with the oxygen-carrying capacity of hemoglobin in infants. This leads to a bluish tint in the skin due to oxygen deprivation.

Correct answer: Stratosphere

The stratosphere houses the ozone layer, which absorbs roughly 97-99% of the Sun's medium-frequency ultraviolet light. Ozone in the troposphere, however, is considered a pollutant and a major component of smog.

Correct answer: Nitrogen and Phosphorus

Runoff carrying fertilizers, detergents, and sewage loads lakes and ponds with nitrogen and phosphorus. These nutrients trigger dense algal blooms, and the decay of the dead algae consumes the dissolved oxygen that fish and other aquatic life need.

Correct answer: Ozone and peroxyacetyl nitrate

Photochemical smog forms when sunlight drives reactions between nitrogen oxides and volatile organic compounds from vehicle exhaust. The products include ground-level ozone and peroxyacetyl nitrate, both strong irritants to the eyes and lungs. Sulfur dioxide with suspended particulates instead characterises classical, reducing smog.

Correct answer: Mercury

Minamata disease is caused by chronic mercury poisoning, specifically through the consumption of fish contaminated with methylmercury. It affects the central nervous system, causing neurological symptoms and birth defects.

Correct answer: The rise in a pollutant's concentration at higher trophic levels

Persistent, fat-soluble toxins such as DDT or methylmercury are passed from prey to predator and are not easily excreted. Their concentration in body tissue therefore rises at each successive trophic level, so top predators carry the heaviest burden.

Correct answer: 5.6

Normal rainwater is slightly acidic with a pH of about 5.6 because carbon dioxide in the air reacts with water to form weak carbonic acid ($H_2CO_3$). Rain with a pH below 5.6 is classified as acid rain.

Correct answer: Potent neurotoxin

Lead is a potent neurotoxin that can cause cognitive impairment, particularly in children, and damage various organ systems. Banning leaded fuel significantly reduced the amount of lead found in the blood of the general population.

Correct answer: Chlorine

Chlorination is a common and effective method for water disinfection. It kills bacteria, viruses, and other microbes by breaking the chemical bonds in their molecules, providing residual protection as water travels through pipes.

Correct answer: Incomplete combustion of fuel in vehicles

Carbon monoxide is produced when fuels are burned with insufficient oxygen. In cities, motor vehicle exhaust is the leading source of this colorless, odorless gas which can be fatal in high concentrations.

Correct answer: Coagulation/Flocculation

Coagulation involves adding chemicals like aluminum sulfate (alum) to water to neutralize the charge of small particles. These particles then clump together into larger masses called 'floc', which can be easily filtered or settled out.

Correct answer: How much heat the gas traps compared with $CO_2$

GWP is a standardized scale used to compare the warming impact of different gases over a specific period. For example, Methane has a GWP much higher than 1, meaning it is far more effective at trapping heat than Carbon Dioxide.

Correct answer: Mottling of teeth and bone deformities

While low levels of fluoride prevent cavities, excessive intake over long periods leads to fluorosis. This causes permanent staining (mottling) of tooth enamel and, in severe cases, painful hardening of bones and joints.

Correct answer: Designing safer, less hazardous chemical processes

Green chemistry, also called sustainable chemistry, focuses on minimizing the environmental impact of chemical manufacturing. It emphasizes waste prevention, atom economy, and the use of safer solvents and renewable feedstocks.

Correct answer: Reaches deep into the lungs and the bloodstream

PM2.5 refers to particles smaller than 2.5 micrometers. Due to their tiny size, they bypass the body's natural defenses in the nose and throat, reaching the alveoli in the lungs and causing cardiovascular and respiratory diseases.