Chemistry: Air and Air pollution

The composition of air is approximately 78% nitrogen, 21% oxygen, and about 0.04% carbon dioxide. The statement that carbon dioxide is 10% is incorrect.

Carbon dioxide (CO₂) is a major greenhouse gas. Its increased concentration in the atmosphere contributes significantly to global warming by trapping heat.

First find the volume of oxygen required for buring the phosporus. First write a balance equation 4P +5O2=2P2O5 . So from the balanced (4x31) =124 phosphorus requirs (5x 22.4)=112dm3 of oxygen. So 15.5gram of phosphorus will require14dm3 of oxygen. Now to get the volume of air that contains 14dm3 of oxygen . we know the air is 20% oxygen. So the volume of air that will contain 14 dm3 of oxygen will be (14x100)/20=70dm3 of air

The air that escapes when water is boiled primarily consists of nitrogen and noble gases, as oxygen and CO₂ are less soluble in water compared to nitrogen.

Freon, a refrigerant, is a halocarbon that can be released into the atmosphere from various sources, contributing to air pollution. It is derived from gaseous hydrocarbons, while argon and neon are inert gases and do not form pollutants.

Carbon monoxide is typically produced by incomplete combustion of carbon-containing fuels and is not a natural component of the atmosphere in significant amounts. Water vapor, nitrogen, and noble gases are naturally occurring in the atmosphere

Argon is commonly used in gas-filled electric bulbs because it is inert and prevents the filament from oxidizing, thereby prolonging the life of the bulb.

Neon is often used in lighting for aerodrome beacons because its bright light can penetrate fog, making it visible even in poor weather conditions.

Noble gases (like helium, neon, argon) are naturally occurring in the atmosphere and are not considered impurities

Efflorescent substances lose water to the air and can become powdery as they dry out. Hydrated sodium carbonate, when exposed to air, can release its water of crystallization, making it efflorescent.

Carbon monoxide (CO) is highly toxic and can be lethal even in small concentrations. It binds to hemoglobin in the blood more effectively than oxygen, preventing oxygen transport

Alkaline pyrogallol absorbs oxygen, making it a suitable reagent for detecting the presence of oxygen in air. None of the other substances listed are used for this purpose

Hydrogen sulfide (H₂S) is often produced through the decomposition of organic matter in sewage and can be released into the air, producing a characteristic rotten egg smell.

Sodium chloride (table salt) is hygroscopic but not deliquescent; it does not absorb enough moisture to dissolve in it. In contrast, sodium hydroxide and calcium chloride are examples of deliquescent substances.

The presence of oxygen does not define air as a mixture. The key reasons include the ability to separate its components and the varying concentrations of gases.

When carbon dioxide is bubbled through lime water, it reacts to form calcium carbonate, which is insoluble and causes the solution to turn milky.

While hydrogen is present in trace amounts in the atmosphere, it is not considered a major natural constituent like nitrogen, carbon dioxide, and noble gases. The primary components of air are nitrogen, oxygen, and noble gases.

Calcium chloride is well-known for its hygroscopic properties, meaning it can absorb moisture from the air. While NaCl (sodium chloride) and NaOH (sodium hydroxide) are also hygroscopic, CaCl₂ is particularly effective at moisture absorption.

Lightning does not produce carbon dioxide; instead, it can cause nitrogen fixation. The other processes listed—respiration, combustion, and decay—do release carbon dioxide into the atmosphere.

When air dissolves in water, the solubility of oxygen is greater than that of nitrogen, so the concentration of nitrogen does not increase.

Potassium hydroxide (KOH) is a strong base that reacts with carbon dioxide (CO₂) to form potassium carbonate. This makes it effective for absorbing CO₂ from the air. The other substances listed do not have this property.

Deliquescent substances absorb moisture from the air and can dissolve in the absorbed water, forming a solution.

Deliquescent compounds absorb moisture from the air and dissolve in it, forming a liquid solution. They do not become solid; rather, they turn into a solution. For example, calcium chloride and sodium hydroxide are deliquescent.

Freon is a brand name for a class of chemicals known as chlorofluorocarbons (CFCs) that are commonly used as refrigerants in air conditioning and refrigeration systems. Neon and argon are noble gases that are not used for this purpose, while boron is a metalloid used in different applications

Both hydrogen sulfide (H₂S) and nitrogen dioxide (NO₂, which can form nitrogen (IV) oxide) can dissolve in rainwater to form acids, contributing to acid rain. CO does not form acid rain directly.

The ozone layer, located in the stratosphere, absorbs the majority of the Sun's harmful ultraviolet (UV) radiation, providing protection for living organisms on Earth. The other options (green, black, freon layers) do not exist in this context.

Lime water is a saturated solution of calcium hydroxide. It is used in various applications, including the detection of carbon dioxide.

Efflorescent substances lose water when exposed to air, resulting in a decrease in weight.

Lime water (calcium hydroxide solution) reacts with carbon dioxide to form calcium carbonate, which turns the solution milky, indicating the presence of carbon dioxide.

Uncovered raw food sold along major roads is likely to contain some amount of lead (Pb) due to air pollution from vehicle emissions. Lead can accumulate on food exposed to the atmosphere, particularly in urban areas with heavy traffic. Other options like silver (Ag), copper (Cu), and sodium (Na) are less likely to be contaminants from air pollution in this contex

Carbon monoxide is odorless and colorless, making it particularly dangerous as it cannot be detected by smell. The "rotten egg" smell is characteristic of hydrogen sulfide, not carbon monoxide

Hygroscopic substances can absorb moisture from the air without dissolving. They remain solid while taking up water vapor. Deliquescent substances, in contrast, absorb moisture and dissolve to form a solution.

Caustic potash is the common name for potassium hydroxide (KOH), a strong alkaline substance used in various chemical applications.

Sodium chloride (table salt) is not hygroscopic and does not effectively absorb water vapor from the air compared to the other substances listed, like calcium chloride and potassium hydroxide.

Carbon dioxide is a natural and essential component of air, while sulfur dioxide, carbon monoxide, and hydrogen sulfide are considered pollutants or impurities.

Calcium chloride is a hygroscopic substance, meaning it readily absorbs water vapor from the air. Therefore, when air passes through it, water vapor is absorbed.

Caustic potash (potassium hydroxide) absorbs CO₂, and alkaline pyrogallol absorbs O₂. Therefore, after passing air through both, only nitrogen and noble gases would remain, as they do not react with these substances.

Krypton and xenon are used in flash tubes because they produce a very bright light when electrically charged, ideal for high-speed photography.

Ozone in the stratosphere absorbs harmful UV radiation from the Sun, protecting living organisms, including humans, from its damaging effects. Carbon dioxide does not provide this protective function, and freon is not naturally present in the atmosphere.

The greenhouse effect refers to the process by which certain gases (greenhouse gases) trap heat in the atmosphere, leading to a rise in Earth's average temperature. This effect is primarily caused by increased levels of CO₂ and other gases due to human activities.

Calcium oxide (quicklime) is not hygroscopic; it is actually a strong desiccant that reacts with water to form calcium hydroxide. It is often used to absorb moisture but does not retain it like hygroscopic substances.

A candle requires oxygen to sustain combustion. As the oxygen in the enclosed space is consumed, the candle will extinguish once the oxygen level falls below the required concentration for combustion.

Hydrogen sulfide can contribute to acid rain formation and is known for its corrosive properties, which can damage building materials. Other pollutants that also contribute to acid rain include sulfur dioxide and nitrogen oxides, but hydrogen sulfide is a notable example

Nitrogen is not a noble gas; it is a diatomic molecule that makes up a significant portion of the atmosphere. Noble gases include helium, argon, and neon, which are unreactive under standard conditions.

Lime water (calcium hydroxide) reacts with carbon dioxide to form calcium carbonate, thus removing CO₂. Alkaline pyrogallol further absorbs oxygen. Therefore, both CO₂ and O₂ are removed from the air

Pollution refers to the introduction of harmful substances or contaminants into the environment, resulting in adverse effects on living organisms and the ecosystem. The other options (greenhouse effect, ozone depletion, global warming) refer to specific environmental issues rather than a general state of impurity.

Nitrogen makes up about 78% of the Earth's atmosphere by volume, making it the most abundant gas. Oxygen follows at approximately 21%, while noble gases and carbon dioxide constitute much smaller fractions.

Chlorofluorocarbons (CFCs) are man-made compounds that release chlorine when they break down in the atmosphere, leading to the destruction of ozone molecules in the ozone layer. Carbon dioxide and hydrogen sulfide do not contribute to ozone depletion.

Oxygen is essential for combustion. It reacts with fuel to produce heat and light. Noble gases do not support combustion, while nitrogen and water vapor do not contribute to the burning process.