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Carbon dioxide (CO2) is composed of molecules where each oxygen atom is covalently double-bonded to a single carbon atom.
Answer: False
Explanation: The molecular structure of carbon dioxide is linear (O=C=O), where the central carbon atom forms double covalent bonds with two oxygen atoms. While each oxygen atom is bonded to only one carbon atom, the statement's phrasing can be interpreted as incomplete. The established description is that the carbon atom is double-bonded to two oxygen atoms.
At room temperature and typical concentrations, carbon dioxide is a colorless gas that possesses a distinct odor.
Answer: False
Explanation: At room temperature and typical concentrations, carbon dioxide is a colorless gas that is odorless. The perception of odor is generally absent at ambient levels.
Carbon dioxide is highly soluble in water and is found dissolved in various bodies of water, including groundwater and oceans.
Answer: True
Explanation: Carbon dioxide exhibits significant solubility in water, leading to its presence in diverse aquatic environments such as groundwater, lakes, and oceans.
Carbon dioxide is lighter than dry air, tending to rise in the atmosphere.
Answer: False
Explanation: Carbon dioxide is approximately 53% denser than dry air, meaning it is heavier and tends to sink rather than rise in the atmosphere.
Carbon dioxide molecules have a bent structure, resulting in a significant electric dipole moment.
Answer: False
Explanation: Carbon dioxide molecules possess a linear structure, not a bent one. This linear and centrosymmetric arrangement results in the molecule lacking an electric dipole moment.
All four vibrational modes of a carbon dioxide molecule are observable in infrared (IR) spectroscopy.
Answer: False
Explanation: Carbon dioxide has four vibrational modes, but only the antisymmetric stretching and bending modes are observable in infrared (IR) spectroscopy. The symmetric stretching mode is typically observed in Raman spectroscopy.
The hydration equilibrium constant (Kh) for carbon dioxide in water at 25°C is approximately 1.70 × 10⁻³.
Answer: True
Explanation: The equilibrium constant for the hydration of carbon dioxide in water at 25°C is indeed reported as approximately 1.70 × 10⁻³.
In neutral or alkaline water (pH > 6.5), carbonic acid is the predominant dissolved CO2 species.
Answer: False
Explanation: In neutral to alkaline water (pH > 6.5), the bicarbonate ion (HCO3⁻) is the predominant dissolved CO2 species, not carbonic acid (H2CO3).
The apparent first acid dissociation constant (pKa1) for carbonic acid is often quoted as 6.35, assuming all dissolved CO2 is present as carbonic acid.
Answer: True
Explanation: An apparent first acid dissociation constant (pKa1) of 6.35 for carbonic acid is frequently cited, based on the assumption that all dissolved CO2 exists as carbonic acid, though the true pKa1 is 3.6.
Dissolving carbon dioxide in desalinated water causes its electrical conductivity to decrease significantly.
Answer: False
Explanation: The dissolution of carbon dioxide in desalinated water leads to a significant increase, not decrease, in its electrical conductivity due to the formation of ions.
Carbon dioxide is considered a weak electrophile, reacting readily with weak nucleophiles.
Answer: False
Explanation: Carbon dioxide is a potent electrophile, comparable in reactivity to compounds like benzaldehyde, and reacts readily with strong nucleophiles, not weak ones.
The redox potential for the reduction of CO2 to CO near pH 7 is approximately -0.53 V versus the standard hydrogen electrode.
Answer: True
Explanation: The standard redox potential for the reduction of carbon dioxide to carbon monoxide near pH 7 is approximately -0.53 V relative to the standard hydrogen electrode.
Solid carbon dioxide, known as dry ice, sublimes at standard atmospheric pressure at temperatures above 0°C.
Answer: False
Explanation: Solid carbon dioxide (dry ice) sublimes at standard atmospheric pressure at a temperature of approximately -78.5°C, well below 0°C.
Carbon dioxide can exist as a liquid at standard atmospheric pressure.
Answer: False
Explanation: Carbon dioxide exists as a solid (dry ice) or a gas at standard atmospheric pressure. It transitions to a liquid state only at pressures significantly above atmospheric pressure (above 5.1 atm).
Carbonia is a crystalline form of carbon dioxide formed under high pressure and low temperature.
Answer: False
Explanation: Carbonia is an amorphous, glass-like solid form of carbon dioxide, produced by supercooling heated CO2 at extreme pressures, not typically described as crystalline or formed under low temperature conditions.
What is the chemical formula for carbon dioxide, and what is its molecular structure?
Answer: CO2, linear structure
Explanation: The chemical formula for carbon dioxide is CO2. Its molecular structure is linear, with the carbon atom double-bonded to two oxygen atoms.
How is carbon dioxide typically described at room temperature and normal concentrations?
Answer: A colorless gas that is odorless
Explanation: At standard room temperature and typical atmospheric concentrations, carbon dioxide exists as a colorless gas and is generally considered odorless.
Where can carbon dioxide be found dissolved in water on Earth?
Answer: In groundwater, lakes, ice caps, and seawater
Explanation: Due to its solubility, carbon dioxide is found dissolved in various terrestrial and oceanic water bodies, including groundwater, lakes, ice caps, and seawater.
How does the density of carbon dioxide compare to dry air?
Answer: It is approximately 53% denser than dry air.
Explanation: Carbon dioxide is notably denser than dry air, being approximately 53% heavier, which influences its behavior in atmospheric conditions.
Why does a carbon dioxide molecule lack an electric dipole moment?
Answer: It has a linear and centrosymmetric structure.
Explanation: A carbon dioxide molecule lacks an electric dipole moment due to its linear and centrosymmetric structure, which causes the bond dipoles to cancel each other out.
Which vibrational modes of CO2 are detectable via IR spectroscopy?
Answer: Antisymmetric stretching and bending modes
Explanation: Infrared (IR) spectroscopy can detect the antisymmetric stretching mode and the degenerate bending modes of a carbon dioxide molecule.
What is the hydration equilibrium constant (Kh) for CO2 in water at 25°C?
Answer: 1.70 × 10⁻³
Explanation: The hydration equilibrium constant (Kh) for carbon dioxide in water at 25°C is approximately 1.70 × 10⁻³.
In water with a pH greater than 6.5 but less than 10.4, which dissolved CO2 species predominates?
Answer: Bicarbonate ion (HCO3⁻)
Explanation: In aqueous solutions with a pH between 6.5 and 10.4, the bicarbonate ion (HCO3⁻) is the predominant species derived from dissolved carbon dioxide.
What happens to the electrical conductivity of desalinated water when carbon dioxide dissolves in it?
Answer: It increases significantly, reaching nearly 30 μS/cm.
Explanation: When carbon dioxide dissolves in desalinated water, it forms carbonic acid, which dissociates into ions, thereby substantially increasing the water's electrical conductivity.
How does carbon dioxide's reactivity compare to other compounds like benzaldehyde?
Answer: It is a potent electrophile, comparable to benzaldehyde.
Explanation: Carbon dioxide exhibits potent electrophilic character, with reactivity levels comparable to benzaldehyde and other strongly electrophilic carbonyl compounds.
What is the common name for solid carbon dioxide, and at what temperature does it sublime at 1 atm?
Answer: Dry ice, at approximately -78.5°C
Explanation: Solid carbon dioxide is commonly known as dry ice, and it undergoes sublimation directly into a gas at approximately -78.5°C (194.65 K) under standard atmospheric pressure.
Under what pressure conditions can carbon dioxide exist as a liquid?
Answer: Above 0.51795 MPa (5.11177 atm)
Explanation: Carbon dioxide transitions to a liquid state only at pressures exceeding its triple point, specifically above approximately 0.51795 MPa (or 5.11177 atm).
Carbon dioxide is opaque to visible light but absorbs infrared radiation, playing a role in regulating Earth's temperature.
Answer: True
Explanation: Carbon dioxide is largely transparent to visible light but effectively absorbs and re-emits infrared radiation, contributing to the greenhouse effect and regulating Earth's thermal balance.
As of July 2025, atmospheric carbon dioxide levels are approximately 428 ppm, which is significantly lower than pre-industrial levels of around 280 ppm.
Answer: False
Explanation: As of July 2025, atmospheric carbon dioxide levels are approximately 428 ppm, which is significantly higher than the pre-industrial levels of around 280 ppm.
Before the Industrial Revolution, atmospheric CO2 levels were primarily regulated by volcanic activity and geological weathering.
Answer: False
Explanation: Prior to the Industrial Revolution, atmospheric CO2 concentrations were regulated by a combination of biological organisms and geological features, not solely by volcanic activity and weathering.
Dissolving carbon dioxide in water forms carbonate and bicarbonate ions, contributing to ocean acidification when atmospheric CO2 rises.
Answer: True
Explanation: The dissolution of carbon dioxide in water leads to the formation of carbonate and bicarbonate ions. An increase in atmospheric CO2 levels results in greater absorption by oceans, causing ocean acidification.
Approximately half of the CO2 emissions released into the atmosphere are absorbed by land and ocean carbon sinks.
Answer: True
Explanation: A significant portion, roughly half, of the carbon dioxide emitted into the atmosphere is absorbed by terrestrial and oceanic carbon sinks, where it is eventually sequestered.
Ocean acidification is primarily caused by the absorption of oxygen by seawater, leading to a decrease in pH.
Answer: False
Explanation: Ocean acidification is primarily caused by the absorption of excess carbon dioxide from the atmosphere, which increases the concentration of hydrogen ions and lowers the pH, rather than by the absorption of oxygen.
Ocean acidification makes it easier for marine calcifying organisms to build shells and skeletons.
Answer: False
Explanation: Ocean acidification reduces the availability of carbonate ions in seawater, making it more difficult, not easier, for marine calcifying organisms like corals and mollusks to construct and maintain their shells and skeletons.
Current atmospheric CO2 concentrations are higher than they have been for approximately 14 million years.
Answer: True
Explanation: Contemporary atmospheric CO2 concentrations are indeed higher than they have been for approximately the last 14 million years, indicating a significant departure from long-term geological norms.
Which statement accurately describes carbon dioxide's interaction with radiation and its atmospheric function?
Answer: It absorbs infrared radiation but is transparent to visible light, acting as a greenhouse gas.
Explanation: Carbon dioxide exhibits transparency to visible light while strongly absorbing infrared radiation. This property allows it to trap heat in the atmosphere, functioning as a significant greenhouse gas.
What is the approximate atmospheric concentration of CO2 as of July 2025, and how does it compare to pre-industrial levels?
Answer: 428 ppm, which is significantly higher than pre-industrial levels
Explanation: As of July 2025, atmospheric CO2 levels are projected to be around 428 ppm, representing a substantial increase compared to the pre-industrial levels of approximately 280 ppm.
What is the main human activity driving the increase in atmospheric CO2?
Answer: The burning of fossil fuels
Explanation: The combustion of fossil fuels is identified as the principal anthropogenic activity responsible for the escalating concentrations of carbon dioxide in the Earth's atmosphere.
How were atmospheric CO2 concentrations regulated before the Industrial Revolution?
Answer: By a combination of organisms and geological features
Explanation: Prior to the Industrial Revolution, atmospheric carbon dioxide levels were regulated by a complex interplay between biological processes involving organisms and various geological mechanisms.
What is the consequence of increased atmospheric CO2 dissolving in oceans?
Answer: Ocean acidification and reduced carbonate ions
Explanation: The absorption of increased atmospheric CO2 by oceans leads to ocean acidification, characterized by a decrease in pH and a reduction in the availability of carbonate ions, which are essential for marine calcifying organisms.
What proportion of atmospheric CO2 emissions is absorbed by land and ocean carbon sinks?
Answer: About half
Explanation: Terrestrial and oceanic carbon sinks collectively absorb approximately half of the carbon dioxide emissions released into the atmosphere, playing a crucial role in mitigating atmospheric CO2 accumulation.
How does ocean acidification negatively impact marine calcifying organisms?
Answer: It reduces the concentration of carbonate ions, hindering shell and skeleton formation.
Explanation: Ocean acidification diminishes the concentration of carbonate ions in seawater, a critical building block for marine calcifying organisms, thereby impeding their ability to form and maintain shells and skeletons.
How does the concentration of CO2 in the atmosphere compare to geological history?
Answer: Current levels are higher than they have been for 14 million years.
Explanation: Contemporary atmospheric CO2 concentrations exceed those observed for approximately the last 14 million years, indicating a significant deviation from long-term geological patterns.
Atmospheric carbon dioxide serves as the primary source of carbon for life on Earth and is a vital part of the carbon cycle.
Answer: True
Explanation: Atmospheric carbon dioxide is fundamental as the primary source of carbon for biological synthesis and plays a critical role in the Earth's carbon cycle.
Photosynthesis, carried out by plants, algae, and cyanobacteria, consumes carbon dioxide and water using sunlight to produce carbohydrates and oxygen.
Answer: True
Explanation: Photosynthesis is the biological process by which plants, algae, and cyanobacteria utilize sunlight, water, and carbon dioxide to synthesize carbohydrates and release oxygen.
Aerobic organisms release carbon dioxide as a byproduct when they convert organic compounds into energy using anaerobic respiration.
Answer: False
Explanation: Aerobic organisms release carbon dioxide as a byproduct of energy conversion through aerobic respiration, which utilizes oxygen, not anaerobic respiration.
Carbonic anhydrase is an enzyme that slows down the conversion of carbon dioxide into carbonic acid within organisms.
Answer: False
Explanation: Carbonic anhydrase is an enzyme that significantly accelerates, rather than slows down, the conversion of carbon dioxide into carbonic acid within biological systems.
In human blood, carbon dioxide is primarily transported as dissolved CO2 in the plasma.
Answer: False
Explanation: While some CO2 is transported dissolved in plasma, the primary mode of carbon dioxide transport in human blood is as bicarbonate ions (HCO3⁻), with carbamino compounds bound to hemoglobin also contributing.
The Haldane Effect explains that increased oxygen binding to hemoglobin reduces the capacity for CO2 transport.
Answer: True
Explanation: The Haldane Effect describes how the saturation of hemoglobin with oxygen influences its affinity for carbon dioxide; increased oxygen binding reduces CO2 transport capacity, facilitating CO2 release in the lungs.
Carbon dioxide acts as a local vasodilator, increasing blood flow to tissues when its concentration rises.
Answer: True
Explanation: Elevated concentrations of carbon dioxide in tissues act as a local vasodilator, causing the expansion of blood vessels and thereby increasing blood flow to supply the metabolically active areas.
Low oxygen levels, rather than high carbon dioxide levels, are the primary stimulus for breathing in humans.
Answer: False
Explanation: In humans, elevated carbon dioxide levels in the blood serve as the primary stimulus for initiating and regulating breathing rate, more so than low oxygen levels.
The typical partial pressure of carbon dioxide in arterial blood is between 35 and 45 mm Hg.
Answer: True
Explanation: The partial pressure of carbon dioxide (PCO2) in arterial blood typically ranges from 35 to 45 mm Hg, reflecting the balance between CO2 production and elimination.
Carbon dioxide levels in the blood are a secondary factor in regulating breathing rate, with oxygen levels being primary.
Answer: False
Explanation: Carbon dioxide levels in the blood are considered the primary factor regulating breathing rate in humans, acting as a more potent stimulus than oxygen levels.
Photosynthesis by phytoplankton consumes atmospheric CO2, thus increasing the amount of CO2 absorbed by the ocean.
Answer: False
Explanation: Photosynthesis by phytoplankton consumes dissolved CO2 in the upper ocean, which in turn promotes the absorption of CO2 from the atmosphere into the ocean, rather than directly increasing the amount of CO2 absorbed.
What is the fundamental role of atmospheric CO2 for life on Earth?
Answer: It is the primary source of carbon for life and a key part of the carbon cycle.
Explanation: Atmospheric carbon dioxide is indispensable as the principal source of carbon for organic molecules synthesized by living organisms and is a central component of the global carbon cycle.
What process do plants, algae, and cyanobacteria use to convert CO2?
Answer: Photosynthesis, using sunlight to create carbohydrates
Explanation: Plants, algae, and cyanobacteria utilize photosynthesis, a process driven by sunlight, to convert carbon dioxide and water into carbohydrates and oxygen.
In aerobic respiration, how is carbon dioxide produced?
Answer: When consuming oxygen to metabolize organic compounds
Explanation: Carbon dioxide is generated as a metabolic byproduct during aerobic respiration when organisms break down organic compounds using oxygen to produce energy.
What is the significance of the enzyme carbonic anhydrase in biological systems?
Answer: It catalyzes the rapid conversion of CO2 to carbonic acid.
Explanation: Carbonic anhydrase is a crucial enzyme that significantly accelerates the reversible reaction between carbon dioxide and water to form carbonic acid, facilitating CO2 transport and buffering in biological systems.
How is carbon dioxide transported in human blood?
Answer: Primarily as bicarbonate ions (70-80%)
Explanation: Carbon dioxide is transported in human blood predominantly as bicarbonate ions (approximately 70-80%), with smaller amounts carried dissolved in plasma (5-10%) and bound to hemoglobin as carbamino compounds (5-10%).
What does the Haldane Effect describe in relation to hemoglobin and CO2 transport?
Answer: How hemoglobin's affinity for CO2 changes with oxygen levels.
Explanation: The Haldane Effect explains that hemoglobin's affinity for carbon dioxide is inversely related to its saturation with oxygen; when hemoglobin binds oxygen, its capacity to bind CO2 decreases, and vice versa.
What is the primary stimulus that triggers breathing in humans?
Answer: High levels of carbon dioxide in the blood
Explanation: The primary physiological stimulus that triggers and regulates the rate of breathing in humans is an increase in the partial pressure of carbon dioxide in the arterial blood.
The primary commercial use of human-produced CO2 is in the production of plastics and synthetic fibers.
Answer: False
Explanation: The vast majority of human-produced CO2 is released into the atmosphere. Commercial uses account for less than 1%, primarily in fertilizer production (urea) and enhanced oil recovery, not plastics and synthetic fibers.
Most CO2 injected for enhanced oil recovery (EOR) is captured from industrial facilities.
Answer: False
Explanation: The majority of carbon dioxide utilized for enhanced oil recovery (EOR) is sourced from naturally occurring underground deposits, although some captured CO2 from industrial processes is also employed.
In greenhouses, carbon dioxide is sometimes added to the atmosphere to enhance plant growth rates.
Answer: True
Explanation: Carbon dioxide enrichment is a common practice in greenhouse cultivation to stimulate and increase plant growth rates by providing a higher concentration for photosynthesis.
In the food industry, carbon dioxide is primarily used as a preservative to prevent spoilage.
Answer: False
Explanation: Within the food industry, carbon dioxide (E290) functions primarily as a propellant and an acidity regulator, rather than a preservative to prevent spoilage.
Dissolved carbon dioxide in beverages contributes a sour taste and the characteristic sensation of carbonation.
Answer: True
Explanation: The dissolution of carbon dioxide in beverages forms carbonic acid, which imparts a sour taste, and also triggers a somatosensory response, creating the distinct sensation of carbonation.
Dry ice is used in winemaking to accelerate fermentation and increase alcohol content.
Answer: False
Explanation: In winemaking, dry ice is utilized to rapidly cool grape clusters, thereby preventing premature fermentation and preserving sugar concentration, or for carbonic maceration, not to accelerate fermentation or increase alcohol content directly.
Carbon dioxide is used in MAG welding, but it can make welds more brittle compared to inert atmospheres.
Answer: True
Explanation: Carbon dioxide serves as a shielding gas in MAG welding, but its reactivity at high temperatures can potentially lead to welds exhibiting increased brittleness compared to those produced under inert gas atmospheres.
Carbon dioxide is commonly used in pneumatic systems because it is flammable and inexpensive.
Answer: False
Explanation: Carbon dioxide is utilized in pneumatic systems and consumer products primarily because it is inexpensive and non-flammable, and it can be liquefied under attainable pressures, allowing for high storage density.
CO2 fire extinguishers extinguish fires by cooling the burning material significantly.
Answer: False
Explanation: Carbon dioxide fire extinguishers primarily function by displacing oxygen, thereby starving the fire. While some cooling occurs, their main extinguishing mechanism is oxygen displacement, not significant cooling of the material.
Supercritical carbon dioxide is used as a solvent in applications like decaffeinating coffee due to its low toxicity.
Answer: True
Explanation: Supercritical carbon dioxide, existing above its critical point, serves as an effective and low-toxicity solvent in various applications, including the decaffeination of coffee beans and in pharmaceutical processing.
Carbon dioxide serves as the lasing medium in early and widely used types of lasers.
Answer: True
Explanation: Carbon dioxide is indeed the active lasing medium in carbon-dioxide lasers, which represent an early and extensively utilized category of laser technology.
What are the primary commercial applications for human-produced CO2?
Answer: Fertilizer production and enhanced oil recovery
Explanation: The principal commercial applications for human-produced carbon dioxide involve its use in the synthesis of fertilizers (e.g., urea) and in enhanced oil recovery (EOR) operations.
What is the primary source of CO2 used in enhanced oil recovery (EOR)?
Answer: Naturally occurring underground deposits
Explanation: The predominant source for carbon dioxide utilized in enhanced oil recovery (EOR) operations is naturally occurring underground reservoirs, rather than captured emissions or industrial processes.
In what way is carbon dioxide utilized in greenhouses?
Answer: To sustain and increase plant growth rates
Explanation: Carbon dioxide is intentionally introduced into greenhouse atmospheres to elevate concentrations, thereby stimulating and enhancing the rate of plant growth through improved photosynthetic efficiency.
What is the function of carbon dioxide as a food additive (E290)?
Answer: Propellant and acidity regulator
Explanation: In the food industry, carbon dioxide, designated as E290 in the EU, primarily serves as a propellant in aerosols and as an acidity regulator, rather than as a sweetener or preservative.
How does dissolved carbon dioxide contribute to the taste and sensation of carbonated beverages?
Answer: It forms carbonic acid, creating a sour taste and carbonation sensation.
Explanation: Dissolved carbon dioxide reacts with water to form carbonic acid, which imparts a characteristic sour taste, and also contributes to the effervescent sensation associated with carbonated beverages.
What is the role of dry ice in winemaking according to the source?
Answer: To prevent premature fermentation and preserve grape quality
Explanation: Dry ice is employed in winemaking primarily to rapidly cool grape clusters, thereby preventing premature fermentation and preserving grape quality, or for carbonic maceration.
What is a potential drawback of using carbon dioxide in MAG welding?
Answer: It can make welds more brittle at high temperatures.
Explanation: A potential disadvantage of using carbon dioxide as a shielding gas in MAG welding is that it can contribute to increased brittleness in the resulting welds, particularly at elevated temperatures.
Why is carbon dioxide a common compressed gas for pneumatic systems?
Answer: It is inexpensive, non-flammable, and easily liquefied.
Explanation: Carbon dioxide is frequently employed as a compressed gas in pneumatic systems and consumer products due to its cost-effectiveness, non-flammable nature, and the ease with which it can be liquefied under moderate pressures, enabling high storage density.
How do CO2 fire extinguishers primarily work?
Answer: By displacing oxygen and starving the fire.
Explanation: Carbon dioxide fire extinguishers operate principally by displacing the surrounding oxygen, thereby depriving the fire of a necessary component for combustion and extinguishing it.
What is supercritical carbon dioxide, and what is one of its applications?
Answer: CO2 above its critical point used as a solvent; application in decaffeinating coffee.
Explanation: Supercritical carbon dioxide refers to CO2 existing above its critical temperature and pressure, where it exhibits properties of both a liquid and a gas, making it an effective solvent used in applications such as decaffeinating coffee.
The Keeling Curve demonstrates the natural, cyclical fluctuations of atmospheric CO2 concentration without showing a long-term trend.
Answer: False
Explanation: The Keeling Curve meticulously tracks atmospheric CO2 concentrations and clearly reveals a significant long-term upward trend, superimposed upon natural seasonal fluctuations, primarily due to anthropogenic emissions.
Jan Baptist van Helmont first identified carbon dioxide as a distinct chemical compound in the 1750s.
Answer: False
Explanation: Jan Baptist van Helmont first described carbon dioxide as a distinct substance, which he termed 'gas' or 'wild spirit,' in the 1640s, not the 1750s.
Joseph Black discovered that 'fixed air' (CO2) was lighter than air and supported combustion.
Answer: False
Explanation: Joseph Black discovered in the 1750s that 'fixed air' (carbon dioxide) was denser than air and could not support flame or life, contrary to the statement.
Humphry Davy and Michael Faraday first liquefied carbon dioxide, while Adrien-Jean-Pierre Thilorier first described solid carbon dioxide.
Answer: True
Explanation: Humphry Davy and Michael Faraday successfully liquefied carbon dioxide in 1823, and Adrien-Jean-Pierre Thilorier provided the first description of solid carbon dioxide (dry ice) in 1835.
What is the significance of the Keeling Curve?
Answer: It tracks atmospheric CO2 concentration, revealing a significant rise due to human activity.
Explanation: The Keeling Curve is a graph that illustrates the continuous measurement of atmospheric carbon dioxide concentration at Mauna Loa Observatory, prominently demonstrating the sustained increase attributed to human activities since 1958.
What historical figure first described carbon dioxide as a discrete substance ('gas' or 'wild spirit')?
Answer: Jan Baptist van Helmont
Explanation: Jan Baptist van Helmont, in the mid-17th century (around the 1640s), was the first to identify and describe carbon dioxide as a distinct substance, which he termed 'gas' or 'wild spirit'.
What did Joseph Black discover about 'fixed air' (CO2) in the 1750s?
Answer: It was denser than air and could not support flame or life.
Explanation: Joseph Black's experiments in the 1750s revealed that 'fixed air' (carbon dioxide) was denser than atmospheric air and incapable of supporting combustion or sustaining life.
Blackdamp, or 'stythe,' is a mixture of oxygen and methane found in mines, historically detected by flame lamps.
Answer: False
Explanation: Blackdamp, also known as stythe, is a suffocating mixture primarily composed of nitrogen and carbon dioxide, not oxygen and methane. Its presence was historically detected by its effect on flame lamps or canaries.
NIOSH recommends an eight-hour Time-Weighted Average exposure limit for carbon dioxide of 5,000 ppm.
Answer: True
Explanation: The National Institute for Occupational Safety and Health (NIOSH) recommends an eight-hour Time-Weighted Average (TWA) exposure limit for carbon dioxide of 5,000 ppm.
Prolonged exposure to CO2 concentrations below 1% is not associated with any significant health effects.
Answer: False
Explanation: Prolonged exposure to CO2 concentrations below 1% (10,000 ppm) can be associated with significant health effects, including headaches, lethargy, cognitive impairment, and emotional irritation, even at levels as low as 0.1% (1000 ppm).
What are the NIOSH Recommended Exposure Limits (REL) for carbon dioxide as an eight-hour Time-Weighted Average (TWA)?
Answer: 5,000 ppm
Explanation: The National Institute for Occupational Safety and Health (NIOSH) has established a Recommended Exposure Limit (REL) for carbon dioxide of 5,000 ppm, calculated as an eight-hour Time-Weighted Average (TWA).
According to studies mentioned in the source, what health effects can prolonged exposure to CO2 below 1% cause?
Answer: Headaches, lethargy, and mental slowness.
Explanation: Prolonged exposure to carbon dioxide concentrations below 1% (10,000 ppm) has been linked to adverse health effects such as headaches, lethargy, reduced cognitive function, and emotional irritability.