Environmental Chemistry-Knowledge-Based Q&A Bank
HSC Chemistry 2nd Paper: Environmental Chemistry (Knowledge-Based Q&A Bank)
Atmospheric Components and Natural Disasters
Question: What is a cyclone?
Answer: A cyclone is a sudden, irregular, and violently rotating wind flow that moves from a high-pressure region toward a low-pressure center.
Question: What is a tidal surge (storm surge)?
Answer: A tidal surge is a phenomenon where massive sea waves swell up and crash violently onto coastal areas with high velocity, caused either by the force of intense cyclonic winds or by underwater earthquakes, landslides, and volcanic eruptions.
Question: What is the Coriolis force?
Answer: As Earth rotates on its axis and revolves in its orbit, a wind flow pattern is generated. This event is called the Coriolis effect. The force generated due to the Coriolis effect that influences cyclones is called the Coriolis force.
Boyle’s and Charles’s Gas Laws
Question: State Boyle’s law.
Answer: At a constant temperature, the volume of a fixed mass of any gas is inversely proportional to the pressure applied to it. That is, V ∝ .
1
P
Question: State Charles’s law in terms of the Kelvin scale.
Answer: At a constant pressure, the volume of a fixed mass of any gas is directly proportional to its absolute temperature or Kelvin temperature. That is, V ∝ T.
Question: State Gay-Lussac’s pressure law.
Answer: At a constant volume, the pressure of a fixed mass of any gas is directly proportional to its absolute temperature. That is, P ∝ T.
Question: State Charles’s law in terms of the Celsius scale.
Answer: At a constant pressure, the volume of a fixed mass of a gas increases or decreases for each degree Celsius rise or fall in temperature by a fraction of of its volume measured at 0°C.
1
273.15
Question: What is an isobaric process?
Answer: An isobaric process is a thermodynamic process in which the pressure of the system remains constant. Plotting the volume of a gas against its absolute temperature results in a straight line passing through the origin.
Question: What is an isobar?
Answer: An isobar is a curve or line on a graph representing the relationship between the volume and temperature of a fixed mass of a gas at a constant pressure.
Question: What is an isothermal process?
Answer: An isothermal process is a thermodynamic process in which the temperature of the system remains constant. Plotting the volume (V) against the inverse of pressure () yields a straight line passing through the origin.
1
P
Question: What is an isotherm?
Answer: An isotherm is a curve on a graph representing the relationship between the pressure and volume of a fixed mass of gas at a constant temperature.
Question: What is an isochore?
Answer: An isochore is a line on a graph representing the relationship between the pressure and temperature of a fixed mass of gas at a constant volume.
Question: What is the Kelvin scale?
Answer: The Kelvin scale (or absolute temperature scale) is a temperature scale designed by Lord Kelvin where absolute zero (-273.15°C) is taken as zero, and the size of each degree interval is equal to one degree Celsius.
Question: What is the absolute temperature scale?
Answer: A scale of temperature considered by taking -273.15°C as 0 K is called the absolute temperature scale.
Question: What is absolute zero temperature?
Answer: The lowest imaginable temperature at which the volume of all gases theoretically becomes zero is called absolute zero temperature.
Question: What is the relational equation between the Celsius and Kelvin scales?
Answer: The relational equation between the Celsius scale and Kelvin scale is: T = (273.15 + t) K.
Mole, Molar Volume, and Avogadro’s Number
Question: State Avogadro’s law.
Answer: Under the same conditions of temperature and pressure, equal volumes of all gases contain an equal number of molecules.
Question: What is Avogadro’s number?
Answer: One mole of any substance contains a specific and constant number of structural particles (atoms, molecules, or ions). This number (6.022 × 1023) is called Avogadro’s number.
Question: What is molar volume?
Answer: The volume occupied by one mole of any gas under specific conditions is called its molar volume.
Question: What is standard temperature?
Answer: Standard temperature is defined as 0 degrees Celsius (or 273.15 Kelvin).
Question: State Gay-Lussac’s pressure law (Alternative statement).
Answer: At a constant volume, the pressure of a fixed mass of gas is directly proportional to its temperature measured on the Kelvin scale. That is, P ∝ T.
Question: What is an isochoric process?
Answer: An isochoric process is a thermodynamic process in which the volume remains constant. Plotting gas pressure against its absolute temperature yields a straight line starting from the origin.
Question: What is an isochore line?
Answer: A line on a graph obtained by plotting the varying values of pressure and temperature for a fixed mass of gas maintained at a constant volume is called an isochore line.
Question: What is STP?
Answer: STP stands for Standard Temperature and Pressure, where temperature is 0°C (or 273.15 K), pressure is 1 atm (or 101.325 kPa), and the molar volume of an ideal gas is 22.414 L.
Question: What is NTP?
Answer: NTP stands for Normal Temperature and Pressure, where temperature is 20°C (or 293.15 K), pressure is 1 atm (or 101.325 kPa), and the molar volume is 24.0548 L.
Question: What is SATP?
Answer: SATP stands for Standard Ambient Temperature and Pressure, where temperature is 25°C (or 298.15 K), pressure is 100 kPa (or 1 bar), and the molar volume is 24.789 L.
Question: What is the Boltzmann constant?
Answer: The Boltzmann constant (k) is the gas constant per molecule, obtained by dividing the universal gas constant (R) by Avogadro’s number (NA). That is, k = .
R
NA
Dalton’s Partial Pressure Law and Graham’s Diffusion Law
Question: State Dalton’s law of partial pressures.
Answer: At a constant temperature, the total pressure exerted by a mixture of non-reacting gases is equal to the sum of the partial pressures of the individual component gases.
Question: What is partial pressure?
Answer: The partial pressure of a gas in a mixture is the pressure that the individual component gas would exert if it alone occupied the entire volume of the mixture at the same temperature.
Question: What is a mole fraction?
Answer: The mole fraction of a component gas in a mixture is the ratio of the number of moles of that component to the total number of moles of all the components present in the mixture.
Question: State Graham’s law of gas diffusion.
Answer: At a constant temperature and pressure, the rate of diffusion of a gas is inversely proportional to the square root of its density. That is, r ∝ .
1
√d
Question: What is diffusion?
Answer: Diffusion is the natural, spontaneous, and uniform mixing of a gas or a liquid into another gas or liquid due to an initial difference in concentration.
Question: What is effusion?
Answer: Effusion is the process in which a gas escapes from a high-pressure zone to a low-pressure zone through a tiny orifice under the influence of external pressure.
Kinetic Theory of Gases and Kinetic Equation
Question: What is the kinetic theory of gases?
Answer: The kinetic theory of gases is a collection of postulates proposed by various scientists to explain the macro-level physical behaviors of gases based on micro-level molecular movements.
Question: What is the kinetic equation of gases?
Answer: Based on the fundamental postulates of the kinetic theory, the mathematical equation established regarding gas pressure is known as the kinetic equation of gases. The equation is:
PV = mNC2
1
3
Question: What is average velocity?
Answer: Average velocity is the mathematical mean of the individual velocities of all the gas molecules present in a gas sample.
Question: What is root-mean-square (RMS) velocity?
Answer: The root-mean-square velocity is defined as the square root of the arithmetic mean of the squares of the velocities of the gas molecules.
Question: What is most probable velocity?
Answer: The most probable velocity is the velocity possessed by the maximum number of molecules in a given gas sample at a specific temperature.
Question: What is the mean free path?
Answer: The average distance traveled by a gas molecule between two successive collisions is called the mean free path.
Ideal Gas vs Real Gas and Critical States
Question: What is an ideal gas?
Answer: A gas that strictly obeys all the gas laws (Boyle’s law, Charles’s law, and Avogadro’s law) at all temperatures and pressures, and perfectly fits the equation PV = nRT, is called an ideal gas.
Question: What is a real gas?
Answer: A gas that does not obey the ideal gas laws perfectly under all conditions of temperature and pressure, meaning it deviates from the equation PV = nRT, is called a real gas.
Question: What is an Amagat curve?
Answer: An Amagat curve is a plot drawn based on the experimentation of scientist Amagat, where the compressibility factor or the product PV of real gases is plotted against pressure P at a constant temperature to exhibit gas deviations.
Question: What is the compressibility factor?
Answer: The compressibility factor (Z) is the ratio of the product of pressure and volume (PV) of a gas to the product of its mole amount, absolute temperature, and the molar gas constant (nRT). That is, Z = .
PV
nRT
Question: What is the Boyle temperature?
Answer: The specific temperature at which a real gas behaves like an ideal gas over an extended, wide range of pressure is called the Boyle temperature.
Question: What is the inversion temperature?
Answer: The inversion temperature is a characteristic temperature for every gas below which the gas cools down upon undergoing adiabatic expansion (Joule-Thomson expansion).
Question: What is critical temperature?
Answer: The critical temperature is the highest characteristic temperature above which a gas cannot be liquefied, no matter how much pressure is applied to it.
Question: What is critical pressure?
Answer: The minimum pressure required to liquefy 1 mol of a gas exactly at its critical temperature is called the critical pressure.
Question: What is critical volume?
Answer: The volume occupied by 1 mol of a gas at its critical temperature and critical pressure is called the critical volume.
van der Waals Equation of State
Question: Write down the van der Waals equation for n moles of gas.
Answer: The van der Waals equation for n moles of a real gas with volume and pressure corrections is:
( P + ) ( V − nb ) = nRT
n2a
V2
Question: Write the van der Waals equation for 11g of O₂ gas.
Answer: Here, the number of moles is n = = 0.3437 mol. Substituting this value, the equation is:
11
32
( P + ) ( V − 0.3437b ) = 0.3437RT
0.1181a
V2
Question: Write the van der Waals equation for 88g of CO₂ gas.
Answer: Here, the number of moles is n = = 2 mol. Substituting this value, the equation is:
88
44
( P + ) ( V − 2b ) = 2RT
4a
V2
Nitrogen Fixation and Nitrogen Cycle
Question: What is the nitrogen cycle?
Answer: The nitrogen cycle is the continuous natural process by which nitrogen and its diverse compounds are interconverted and circulated between the environment and living organisms.
Question: What is nitrogen fixation?
Answer: The chemical or biological process by which atmospheric nitrogen gas is converted into ammonia (NH3) or other usable nitrogenous compounds to be absorbed by plants is called nitrogen fixation.
Question: What is a lightning strike?
Answer: A lightning strike is a massive electrical discharge caused by the high-velocity collision of clouds carrying opposite electric charges. During a strike, the local temperature spikes to around 3000°C.
Greenhouse Effect, Smog, and Acid Rain
Question: What is a greenhouse gas?
Answer: Greenhouse gases are atmospheric gaseous components that trap infrared thermal radiation emitted from the Earth’s surface, preventing it from escaping into space and thereby keeping the planet warm.
Question: What is CFC?
Answer: CFC stands for Chlorofluorocarbon, which refers to the volatile chlorine and fluorine-substituted derivatives of methane and ethane.
Question: What is Freon?
Answer: Freon is the commercial trade name for chlorofluorocarbons (CFCs), widely used as refrigerants and propellents.
Question: What is phosgene gas?
Answer: Phosgene (COCl2) is a highly toxic, suffocating gas produced when carbon monoxide (CO) reacts with chlorine gas (Cl2) under the influence of sunlight.
Question: What is photochemical smog?
Answer: Photochemical smog is a hazardous brown haze formed in the atmosphere when volatile organic compounds (VOCs) and nitrogen oxides (NOx) react together under the presence of solar radiation.
Question: What is global warming?
Answer: Global warming is the gradual increase in the average temperature of the Earth’s atmosphere and oceans, primarily driven by the excessive release of greenhouse gases from burning fossil fuels.
Question: What is acid rain?
Answer: Acid rain is any form of precipitation or rainfall that contains acidic components, where the pH value falls below 5.6 due to atmospheric industrial pollution.
Question: What is chlorosis?
Answer: Chlorosis is a plant disease condition where the chlorophyll production process of leaves is inhibited due to the toxic presence of sulfur oxides (SOx) in the air, leading to the loss of their natural green color.
Acid-Base Concepts and Theories
Question: What is an acidic oxide?
Answer: An acidic oxide is an oxide of a non-metal that reacts with water to form an acid, or reacts with bases to produce salt and water.
Question: What is an acid according to the Arrhenius theory?
Answer: According to the Arrhenius theory, an acid is any hydrogen-containing substance that dissociates in an aqueous solution to produce hydrogen ions (H+).
Question: What is a base according to the Arrhenius theory?
Answer: According some chemical perspectives, a base is a substance that dissociates in aqueous solution to yield hydroxyl ions (OH−).
Question: Write down the fundamental definition of the Arrhenius acid-base theory.
Answer: An acid is a compound that yields hydrogen ions (H+) in an aqueous solution, whereas a base is a compound that yields hydroxide ions (OH−) in an aqueous solution.
Question: What is an acid according to the Brønsted-Lowry theory?
Answer: According to the Brønsted-Lowry protonic concept, an acid is a chemical species (molecule or ion) capable of donating a proton (H+) to another species.
Question: What is a base according to the Brønsted-Lowry theory?
Answer: According to the Brønsted-Lowry theory, a base is any chemical species capable of accepting a proton (H+) from another species.
Question: What is a monoprotic acid?
Answer: A monoprotic acid is an acid that can donate only one proton per molecule during dissociation (e.g., HCl).
Question: What is a monoprotic base?
Answer: A monoprotic base is a basic chemical species capable of accepting only a single proton during a reaction.
Question: What is a strong base?
Answer: A strong base is a basic compound that fully and completely ionizes or dissociates into its constituent ions in an aqueous solution.
Question: What is a weak acid?
Answer: A weak acid is an acid that ionizes only partially (typically around 1-2%) in an aqueous solution at normal concentrations.
Question: What is a weak base?
Answer: A weak base is a basic compound that dissociates or ionizes only to a very small extent in an aqueous solution.
Question: What is the basicity of an acid?
Answer: The basicity of an acid is the number of replaceable or donatable hydrogen ions (H+) present per molecule of that acid.
Question: What is the acidity of a base?
Answer: The acidity of a base refers to the total number of replaceable hydroxyl groups (OH−) present per molecule of that base.
Question: What is a conjugate base?
Answer: A conjugate base is the chemical species formed remaining after an acid has donated or lost a proton (H+).
Question: What is a conjugate acid?
Answer: A conjugate acid is the chemical species formed when a base gains or accepts a proton (H+).
Question: What is an acid according to the Lewis theory?
Answer: According to the Lewis electronic theory, an acid is a chemical species capable of accepting an electron lone pair from a donor.
Question: What is a base according to the Lewis theory?
Answer: According to the Lewis theory, a base is a chemical species capable of donating an electron lone pair to an acceptor.
Aqueous Chemistry and Water Quality Criteria (DO, BOD, COD, TDS)
Question: What is surface water?
Answer: Surface water refers to any open body of water found on the Earth’s crust, such as rivers, canals, streams, lakes, and ponds.
Question: What is pure water?
Answer: Pure water is water that is transparent, colorless, odorless, free of any suspended organic or inorganic toxic impurities, and free of pathogenic microorganisms.
Question: What is hard water?
Answer: Hard water is freshwater that contains a high concentration of dissolved divalent cations, primarily calcium (Ca2+), magnesium (Mg2+), and iron (Fe2+).
Question: What is hardness of water?
Answer: Hardness of water is the specific property or characteristic of water caused by dissolved divalent metallic cations that prevents the easy formation of lather with soap.
Question: What causes permanent hardness in water?
Answer: Permanent hardness in water is caused by the presence of dissolved chloride and sulfate salts of calcium, magnesium, or iron. It cannot be removed by boiling.
Question: What causes temporary hardness in water?
Answer: Temporary hardness in water is caused by the presence of dissolved bicarbonate salts of calcium and magnesium. It can be easily removed by boiling.
Question: What is pH?
Answer: pH is defined as the negative logarithm of the molar concentration of hydrogen ions (H+) in a solution. The standard safe pH limit for drinking water is 6.7 – 7.4.
Question: What is DO?
Answer: DO stands for Dissolved Oxygen, which represents the total mass or concentration of free gaseous oxygen dissolved naturally in a water sample at a specific temperature.
Question: What is BOD?
Answer: BOD stands for Biochemical Oxygen Demand, which is the amount of dissolved oxygen required by aerobic microorganisms (bacteria) at 20°C over a period of 5 days to biologically decompose the biodegradable organic matter present in a water sample.
Question: What is COD?
Answer: COD stands for Chemical Oxygen Demand, which is the total mass of oxygen required to chemically oxidize both biodegradable and non-biodegradable organic pollutants present in a unit volume of water sample into CO2, NH3, H2S, and H2O.
Question: What is TDS?
Answer: TDS stands for Total Dissolved Solids, which indicates the combined total weight of all inorganic salts and small amounts of organic matter dissolved completely in a given volume of filtered water.
Question: What is TOC?
Answer: TOC stands for Total Organic Carbon, a metric used to evaluate water cleanliness by measuring the carbon bound within organic compounds. The ideal TOC for highly pure water is 0.05 mg/L.
Question: What is TLV?
Answer: TLV stands for Threshold Limit Value, which represents the maximum concentration threshold of an environmental pollutant below which it is safe, but exceeding it causes adverse, hazardous biological impacts on living organisms.
Question: What is water pollution?
Answer: Water pollution is the hazardous degradation of the physical, chemical, and biological properties of water due to the introduction of harmful foreign substances, making it dangerous for consumption and ecosystem survival.
Industrial Waste and Heavy Metals in Food Chain
Question: What is industrial waste?
Answer: Industrial waste is the unwanted residual or discarded byproduct material generated from industrial activities, raw material processing, manufacturing chemical reactions, and separation processes.
Question: What is industrial liquid effluent?
Answer: Industrial liquid effluent is the hazardous liquid mixture discarded from factories containing raw material chemical processing residues, industrial chemical byproducts, and toxic liquids.
Question: What is arsenicosis?
Answer: Arsenicosis is a chronic systemic medical condition or disease caused by the prolonged consumption of drinking water contaminated with toxic levels of arsenic.
Question: What is a heavy metal?
Answer: Heavy metals are metallic elements with relatively high densities or specific gravity greater than 5 (e.g., As, Hg, Pb, Cd) that show high systemic toxicity at trace levels.
Question: What is bioaccumulation?
Answer: Bioaccumulation is the progressive process whereby non-biodegradable toxic substances or heavy metals accumulate inside the tissues of a living organism over time through the food chain, eventually crossing dangerous thresholds.
Question: What is a primary pollutant?
Answer: A primary pollutant is an air polluting chemical emitted directly into the atmosphere from an identifiable source (e.g., carbon monoxide from exhaust).
Question: What is a secondary pollutant?
Answer: A secondary pollutant is not emitted directly, but forms in the air when primary pollutants react or interact with other normal atmospheric components.
Question: What is a hygroscopic substance?
Answer: A hygroscopic substance is a solid, liquid, or gaseous material that absorbs water vapor from the surrounding air when exposed, but does not dissolve completely to form a liquid solution.
Question: What is a solution?
Answer: A solution is a homogeneous mixture composed of two or more substances where the individual chemical identities and properties are uniformly blended.
Question: What is an environmental pollutant?
Answer: An environmental pollutant is any substance whose concentration in the ecosystem exceeds normal tolerance levels, resulting in severe disruption to the normal lifecycle of living organisms.
Question: What is air pollution?
Answer: Air pollution is the harmful alteration of atmospheric air quality caused by the excessive buildup of foreign gases, particulate matter, or biological molecules from natural or anthropogenic activities.
