Free Environmental Chemistry MCQs with Answers

211. Thermal processing of industrial waste material aims at:

• A. Burning of waste material in pits
• B. Converting the solid waste into useful products by thermal treatment
• C. Energy recovery from organic matter prior to its final disposal
• D. Size reduction and compaction by thermal process

Explanation: The primary function of thermal treatment is to convert the waste to a stable and usable end product. Therefore the answer will be B.

212. Which one is not a nitrogenous fertilizer?

• A. Ammonium nitrate
• B. Triple phosphate
• C. Urea
• D. Nitro phosphate

Explanation: The correct answer is Triple phosphate. It is a phosphate fertilizer, primarily providing phosphorus rather than nitrogen. Ammonium nitrate, Urea, and Nitro phosphate all contain nitrogen, making them nitrogenous fertilizers. While Nitro phosphate is not primarily used as a fertilizer, it still contains nitrogen, which disqualifies it as the correct answer in this context.

213. The amount of methane in biogas is approximately:

• A. 10-30%
• B. 50-90%
• C. 50-75%
• D. 60-75%

Explanation: Biogas is predominantly composed of methane (CH4) and carbon dioxide (CO2). The methane content typically ranges from 50% to 75% by volume. Option C accurately reflects this range. Option A suggests a much lower methane content than is typical, Option B overestimates the possible upper limit, and Option D does not encompass the full typical range, omitting the lower end.

214. The basic principle of green chemistry is/are:

• A. To prevent waste creation
• B. To maximize the atom economy
• C. To create less hazardous synthetic chemical
• D. All of the above

Explanation: The basic principles of green chemistry encompass all the options listed: A. To prevent waste creation - This is a key principle of green chemistry. It aims to minimize or eliminate the generation of waste products in chemical processes. B. To maximize the atom economy - This principle emphasizes using synthetic methods that incorporate as many atoms of the starting materials as possible into the final product, reducing waste. C. To create less hazardous synthetic chemicals - Green chemistry promotes the development and use of chemicals that are less toxic and hazardous to human health and the environment. Therefore, all of these principles (A, B, and C) are correct and collectively represent the fundamental goals of green chemistry. So the correct option is d.

215. What is the most important source of water pollution in Pakistan?

• A. Industries
• B. Transportation
• C. Mining Industry
• D. Agricultural and municipal wastage

Explanation: Contamination of water bodies is called water pollution. Pakistan is an agricultural country. The root cause of water pollution in Pakistan arises here. The farmers use tons of water for their fields and crops and then dump all the contaminated water into lakes and rivers. In addition to that, the municipal committees are least bothered about the pollution caused by the garbage they throw in the water bodies. The industries also play a role in this, but the formerly mentioned points are the main causes of destruction. Thus, we will go for option D.

216. Water is said to be permanently hard when it contains:

• A. carbonates of Ca2+ and Mg2+ ions
• B. Bicarbonates of Ca2+ and Mg2+ ions
• C. sulphates of Na+ and Mg2+ ions
• D. chlorides of Ca2+ and Mg2+ ions

Explanation: The presence of soluble salts of calcium and magnesium, i.e., sulfates and chlorides of calcium and magnesium, causes permanent hardness in the water.

217. Commonly used coagulant used for the purification of water is:

• A. Ca(NO3)2
• B. MgCl2
• C. Al2(SO4)3
• D. Ca(OH)2

Explanation: In water treatment, coagulants like Al2(SO4)3 (aluminum sulfate) are used to remove impurities by causing them to aggregate for easier removal. This process is essential for removing organic matter, pathogens, and toxic materials. Ca(NO3)2 is a fertilizer, MgCl2 is used for de-icing, and Ca(OH)2 is used for pH adjustment, not as a primary coagulant.

218. Drinking water should be odorless, tasteless and live from turbidity and its pH should range between:

• A. 6.0 to 7.0
• B. 7.0 to 8.5
• C. 4.5 to 6.0
• D. 8.5 to 9.0

Explanation: It is recommended that the pH of drinking water should be between 6.5-8.5 on a scale that ranges from 0 - 14, hence the answer will be B.

219. The presence of microorganisms in drinking water is determined by:

• A. COD
• B. TOC
• C. BOD
• D. TDS

Explanation: Biochemical oxygen demand (BOD) is a chemical procedure for determining the amount of dissolved oxygen needed by microorganisms in a body of water to break down organic material present in a given water sample at a certain temperature over a specific period. The greater the value of BOD, the more rapidly oxygen is depleted in water bodies. This means less oxygen is available to higher forms of aquatic life.

220. Amongst the following, which compounds control the tooth decay:

• A. An Iodide compound
• B. A bromide compound
• C. A chloride compound
• D. A fluoride compound

Explanation: Fluoride is a compound that helps prevent tooth decay by strengthening tooth enamel and making it more resistant to acid attacks from bacteria. It can be found in toothpaste, mouthwash, and even in some drinking water sources. Fluoride ions replace hydroxide ions in the enamel, forming a more stable compound that is less susceptible to decay. Iodide, chloride, and bromide are not as effective in preventing tooth decay as fluoride.