Uses and environmental effects of haloalkanes — NEET & JEE Questions

Question 1 · difficulty L1 · recall

Chlorofluorocarbons are environmentally important because they can contribute to

• A. stratospheric ozone depletion
• B. formation of extra atmospheric oxygen
• C. elimination of greenhouse effects
• D. conversion of nitrogen into ozone

Question 2 · difficulty L2 · understanding

Why were many haloalkanes historically useful as solvents?

• A. They can dissolve many organic substances and some are relatively nonflammable
• B. They are all strongly ionic and water-soluble
• C. They all react instantly with air
• D. They are all harmless to humans and the environment

Question 3 · difficulty L2 · understanding

DDT is environmentally problematic mainly because it is

• A. persistent and can biomagnify through food chains
• B. rapidly biodegradable within minutes
• C. a harmless nutrient for wildlife
• D. unable to accumulate in organisms

Question 4 · difficulty L2 · understanding

The ozone-depleting action of CFCs becomes important after they

• A. reach the stratosphere and undergo photochemical breakdown
• B. dissolve completely in ocean water at ground level
• C. react only with nitrogen in soil
• D. are converted directly into carbon dioxide in refrigerators

Question 5 · difficulty L3 · understanding

Choose the correct sequence of reagents in the conversion of 4-nitrotoluene to 2-bromotoluene.

• A. $$\mathrm{NaNO}_2 / \mathrm{HCl} ; \mathrm{Sn} / \mathrm{HCl} ; \mathrm{Br}_2 ; \mathrm{H}_2 \mathrm{O} / \mathrm{H}_3 \mathrm{PO}_2$$
• B. $$\mathrm{Sn} / \mathrm{HCl} ; \mathrm{NaNO}_2 / \mathrm{HCl} ; \mathrm{Br}_2 ; \mathrm{H}_2 \mathrm{O} / \mathrm{H}_3 \mathrm{PO}_2$$
• C. $$\mathrm{Br}_2 ; \mathrm{Sn} / \mathrm{HCl} ; \mathrm{NaNO}_2 / \mathrm{HCl} ; \mathrm{H}_2 \mathrm{O} / \mathrm{H}_3 \mathrm{PO}_2$$
• D. $$\mathrm{Sn} / \mathrm{HCl} ; \mathrm{Br}_2 ; \mathrm{NaNO}_2 / \mathrm{HCl} ; \mathrm{H}_2 \mathrm{O} / \mathrm{H}_3 \mathrm{PO}_2$$

Question 6 · difficulty L3 · application

Which property helps explain why some halogenated compounds were used in fire-extinguishing applications?

• A. Low flammability
• B. Extremely high combustibility
• C. Rapid oxidation in air
• D. Ability to supply oxygen

Question 7 · difficulty L3 · application

A pesticide remains in soil for years and its concentration increases at higher trophic levels. Which environmental behaviour is being described?

• A. Persistence with biomagnification
• B. Rapid biodegradation
• C. Dilution without accumulation
• D. Ozone formation

Question 8 · difficulty L3 · application

Why can a chemically stable CFC still become environmentally reactive in the upper atmosphere?

• A. High-energy UV radiation can cleave bonds and generate radicals
• B. Stability means it can never react under any condition
• C. Gravity converts it into chlorine gas
• D. It becomes ionic only because pressure is low

Question 9 · difficulty L4 · application

Which sequence best represents the ozone-depletion role of a CFC?

• A. CFC reaches stratosphere → UV releases chlorine radical → chlorine participates in catalytic ozone destruction
• B. CFC dissolves in rain → produces oxygen → ozone increases
• C. CFC burns in soil → nitrogen disappears → ozone decreases
• D. CFC reacts with ozone only once and chlorine is permanently consumed

Question 10 · difficulty L4 · application

Why are persistent, fat-soluble halogenated pollutants especially concerning for top predators?

• A. Their concentrations can increase through successive trophic levels
• B. Top predators never ingest pollutants
• C. Fat solubility guarantees rapid excretion
• D. Persistence prevents uptake by organisms