Environmental chemistry practice · Mixed difficulty

Option C ($NO$) is correct because Nitrogen oxides (NOx) are major components of photochemical smog and cause irritation to the nose and throat.

Option C (Skin cancer) is correct because depletion of the ozone layer increases the amount of harmful UV radiation reaching the Earth's surface, which is a major cause of skin cancer.

Option B (Freons and chlorofluorocarbons are inert. Chemically, they do not react with ozone in stratosphere.) is correct because CFCs are unreactive in the troposphere, allowing them to reach the stratosphere where they are broken down by UV light, releasing chlorine radicals that deplete ozone.

Option B (A combination of smoke and fog) is correct because smog is defined as a mixture of smoke and fog in the atmosphere.

Option A (Acrylic rubber and liquid nitrogen tetraoxide) is correct because these are commonly used propellants in hybrid rockets.

Option D (acid rain) is correct because acid rain, containing sulfuric and nitric acids, reacts with the calcium carbonate in marble, causing it to dissolve and discolor.

Option B (Carcinogens) is correct because DDT and BHC are known to have carcinogenic properties.

Option C (${\mathrm{O}_2}$) is correct because oxygen does not significantly absorb infrared radiation and therefore does not contribute to the greenhouse effect.

Option D (Winter during morning time) is correct because London smog (also known as classical smog) forms in cold, humid conditions during winter mornings due to the accumulation of smoke and sulfur dioxide.

Option A ($\mathrm{O}_3$) is correct because ozone is always formed during the photochemical smog formation process due to the reaction of oxygen atoms with oxygen molecules.

Option B (Increase with time) is correct because initially, the concentration of products is low, so the reaction quotient (Q) is low and increases as the reaction proceeds.

The correct answer is B (Carbon monoxide- $Hb$) because carbon monoxide binds to hemoglobin with much greater affinity than oxygen, leading to a toxic effect by preventing oxygen transport.

Option A (0.2 ppm) is correct because the maximum prescribed concentration of iron (Fe) in drinking water is 0.2 ppm according to established guidelines.

Option D (Safe for teeth) is correct because fluoride ions at a concentration of up to 1 ppm in drinking water are beneficial for dental health.

Option A (Will cause increase in cases of skin diseases) is correct because increased UV radiation exposure is a known cause of skin diseases, including skin cancer.

Option C (500―1000 nm) is correct because the size of particulates of ${\mathrm{H}_2}\mathrm{S}{\mathrm{O}_4}$ fog lies in the range of 500-1000 nm.

Option B ($CO_2$) is correct because while $CO_2$ can contribute to climate change at high concentrations, it is not typically regarded as a pollutant at normal atmospheric levels.

Option D (Hydrocarbons) is correct because volcanic eruptions primarily emit gases like sulfur dioxide, hydrogen sulfide, and carbon monoxide, but not significant amounts of hydrocarbons.

Option B (Industrial wastes) is correct because industrial effluents often contain a wide variety of pollutants, including heavy metals and toxic chemicals, making them a significant source of water pollution.

Option B (Biodegradable pollutants) is correct because sewage primarily consists of organic waste that can be decomposed by microorganisms.

Option A (Action of UV rays on oxygen) is correct because ozone in the upper atmosphere is formed when UV radiation from the sun splits oxygen molecules (O2) into individual oxygen atoms, which then combine with other O2 molecules to form ozone (O3).

Option A ($CO$) is correct because carbon monoxide is the primary pollutant released from automobile exhaust due to incomplete combustion.

Option A (Organic pollutant in water) is correct because BOD measures the amount of oxygen required to decompose organic matter in water.

Option B (Burning garbage) is correct because burning garbage often contains mercury-containing items, leading to mercury emissions.

Option D (All of the above) is correct because $SO_2$ contributes to respiratory issues, acid rain, and corrosion of building materials.

Option C (Winter during morning time) is correct because London smog, also known as classical smog, typically occurs during winter mornings due to coal combustion and temperature inversions.

Option B ($\mathrm{H}_2 \mathrm{SO}_4$) is correct because sulfuric acid is a major component of acid rain and reacts with the calcium carbonate in marble.

Option B (Kill germs) is correct because chlorine is added to water to disinfect it by killing bacteria and other microorganisms.

Option A ($5\mathrm{ }ppm$) is correct because a dissolved oxygen level of 5 ppm is generally considered necessary for a healthy aquatic ecosystem.

Option C (Micro-organisms present in the soil) is correct because soil microorganisms can oxidize CO to CO2, effectively removing it from the atmosphere.