Co2

What is the chemical formula of carbon dioxide?
a) CO
b) CO₂
c) C₂O
d) C₂O₂
✅ b) CO₂
Explanation: CO₂ consists of one carbon atom and two oxygen atoms.
(BPSC 2015)
Which gas turns lime water milky?
a) Oxygen
b) Nitrogen
c) Carbon dioxide
d) Hydrogen
✅ c) Carbon dioxide
Explanation: CO₂ reacts with Ca(OH)₂ (lime water) to form insoluble CaCO₃.
(BPSC CDPO 2021)
Carbon dioxide is mainly released by:
a) Plants at night
b) Industrial units
c) Vehicles
d) All of the above
✅ d) All of the above
Explanation: All these sources emit CO₂ through respiration or combustion.
(BPSC 67th Prelims)
Which of the following is a greenhouse gas?
a) Argon
b) Helium
c) Carbon dioxide
d) Neon
✅ c) Carbon dioxide
Explanation: CO₂ traps infrared radiation and contributes to the greenhouse effect.
(BPSC 65th)
The gas used in fire extinguishers is:
a) Oxygen
b) Nitrogen
c) Carbon dioxide
d) Methane
✅ c) Carbon dioxide
Explanation: CO₂ cuts off oxygen and helps extinguish flames.
(BPSC Assistant 2017)
Carbon dioxide is released during:
a) Photosynthesis
b) Respiration
c) Water cycle
d) Nitrogen fixation
✅ b) Respiration
Explanation: CO₂ is a by-product of aerobic respiration.
(BPSC 63rd)
What is the main cause of ocean acidification?
a) CO
b) CO₂
c) CH₄
d) NH₃
✅ b) CO₂
Explanation: CO₂ dissolves in seawater, forming carbonic acid, lowering pH.
(BPSC 64th)
What happens when excess CO₂ accumulates in the atmosphere?
a) Global warming
b) Acid rain
c) Depletion of ozone
d) None
✅ a) Global warming
Explanation: CO₂ enhances heat retention in the atmosphere.
(BPSC Teacher 2023)
Which gas is released during combustion of fossil fuels?
a) CO₂
b) H₂
c) N₂
d) O₂
✅ a) CO₂
Explanation: Carbon in fuels combines with O₂ to form CO₂ during burning.
(BPSC 66th)
Which of the following is not a property of CO₂?
a) Supports combustion
b) Colorless
c) Odorless
d) Heavier than air
✅ a) Supports combustion
Explanation: CO₂ actually inhibits combustion; it is used in fire suppression.
(BPSC 2020)

NCERT-Based MCQs (Q11–30)

Carbon dioxide is:
a) Inflammable
b) A reducing agent
c) Used in baking
d) All of the above
✅ d) All of the above
Explanation: It is non-flammable, used as leavening agent, and acts as a mild reducing agent.
Which process removes carbon dioxide from the air?
a) Photosynthesis
b) Respiration
c) Combustion
d) Fermentation
✅ a) Photosynthesis
Explanation: Plants absorb CO₂ and release oxygen during photosynthesis.
CO₂ is used to prepare which fizzy drinks?
a) Fruit juices
b) Soft drinks
c) Tea
d) Milk
✅ b) Soft drinks
Explanation: CO₂ is used to carbonate beverages.
Which organ in the human body helps eliminate carbon dioxide?
a) Heart
b) Liver
c) Lungs
d) Kidneys
✅ c) Lungs
Explanation: Lungs remove CO₂ during exhalation.
Which of the following contributes most to atmospheric CO₂?
a) Lightning
b) Photosynthesis
c) Fossil fuel combustion
d) Volcanic eruption
✅ c) Fossil fuel combustion
Explanation: Burning coal, oil, and gas releases large amounts of CO₂.
CO₂ is heavier than air. This means:
a) It rises quickly
b) It is used in hot air balloons
c) It collects in lower areas
d) It causes suffocation in oxygen
✅ c) It collects in lower areas
Explanation: Being denser, it settles and may cause asphyxiation in confined spaces.
Green plants use carbon dioxide to form:
a) Water
b) Oxygen
c) Glucose
d) Chlorophyll
✅ c) Glucose
Explanation: CO₂ and water are used to synthesize glucose via photosynthesis.
The dry ice is:
a) Frozen oxygen
b) Solid carbon dioxide
c) Compressed nitrogen
d) Solidified methane
✅ b) Solid carbon dioxide
Explanation: Dry ice sublimates directly into gas without melting.
Which acid is formed when CO₂ dissolves in water?
a) Nitric acid
b) Sulfuric acid
c) Carbonic acid
d) Hydrochloric acid
✅ c) Carbonic acid
Explanation: CO₂ + H₂O → H₂CO₃ (a weak acid)
Excess CO₂ in blood leads to:
a) Alkalosis
b) Hypoxia
c) Acidosis
d) Hypercalcemia
✅ c) Acidosis
Explanation: High CO₂ increases blood acidity, affecting pH.
CO₂ is used in photosynthesis in the:
a) Roots
b) Stem
c) Leaves
d) Flowers
✅ c) Leaves
Explanation: Chloroplasts in leaves absorb CO₂ for photosynthesis.
CO₂ can be detected by turning lime water:
a) Pink
b) Milky
c) Colorless
d) Yellow
✅ b) Milky
Explanation: Ca(OH)₂ + CO₂ → CaCO₃ (white precipitate).
CO₂ is released during fermentation by:
a) Plants
b) Bacteria
c) Fungi
d) Viruses
✅ c) Fungi
Explanation: Yeast (fungi) release CO₂ during anaerobic fermentation.
What is the approximate percentage of CO₂ in Earth's atmosphere?
a) 0.03%
b) 1%
c) 5%
d) 10%
✅ a) 0.03%
Explanation: It’s present in trace amounts but highly influential in climate.
Carbon dioxide is non-supportive of life because:
a) It’s toxic
b) It displaces oxygen
c) It corrodes cells
d) It dissolves tissue
✅ b) It displaces oxygen
Explanation: In confined spaces, CO₂ accumulation can cause suffocation.
Which plant absorbs maximum CO₂?
a) Banyan
b) Neem
c) Peepal
d) Mango
✅ c) Peepal
Explanation: Peepal trees are known for high oxygen output and CO₂ absorption.
Carbon dioxide is essential for:
a) Combustion
b) Photosynthesis
c) Corrosion
d) Polymerization
✅ b) Photosynthesis
Explanation: It's a key reactant in food-making process of plants.
Which of the following has the highest CO₂ footprint?
a) Solar energy
b) Wind energy
c) Coal-based power
d) Hydro energy
✅ c) Coal-based power
Explanation: Burning coal releases massive CO₂ emissions.
Which process in living beings generates CO₂?
a) Digestion
b) Excretion
c) Respiration
d) Circulation
✅ c) Respiration
Explanation: CO₂ is the end-product of glucose oxidation in cells.
How does CO₂ cause greenhouse effect?
a) Blocks UV rays
b) Traps infrared heat
c) Blocks sunlight
d) Produces ozone
✅ b) Traps infrared heat
Explanation: It prevents heat from escaping, warming the planet.
Which of the following industries releases maximum CO₂?
a) Textile
b) Cement
c) Paper
d) Leather
✅ b) Cement
Explanation: Cement production releases large amounts of CO₂ during limestone calcination and fuel burning.
In which form is CO₂ stored in soft drink bottles?
a) Solid
b) Liquid under pressure
c) Dry gas
d) Aerosol
✅ b) Liquid under pressure
Explanation: CO₂ is pressurized and dissolved in the drink as a liquid; it forms bubbles when pressure is released.
What is the main source of indoor CO₂ accumulation?
a) Air conditioners
b) Respiration
c) Paint
d) Detergents
✅ b) Respiration
Explanation: Human and animal respiration release CO₂ indoors, especially in poorly ventilated spaces.
Which of these processes does not release CO₂?
a) Respiration
b) Combustion
c) Photosynthesis
d) Fermentation
✅ c) Photosynthesis
Explanation: Photosynthesis consumes CO₂ to produce oxygen and glucose.
Which gas is responsible for fizz in soda?
a) Nitrogen
b) Hydrogen
c) Oxygen
d) Carbon dioxide
✅ d) Carbon dioxide
Explanation: Soda is carbonated using CO₂ under high pressure.
What is the role of carbon dioxide in fire extinguishers?
a) Oxidizes fire
b) Cools surroundings
c) Displaces oxygen
d) Forms water
✅ c) Displaces oxygen
Explanation: CO₂ smothers the fire by cutting off oxygen supply.
What happens to CO₂ during photosynthesis?
a) It is oxidized
b) It is broken into carbon and oxygen
c) It combines with water to form glucose
d) It remains unchanged
✅ c) It combines with water to form glucose
Explanation: Plants convert CO₂ and H₂O into glucose and oxygen using sunlight.
What is the main danger of CO₂ in closed spaces?
a) Explosion
b) Toxic reaction
c) Asphyxiation
d) Odor emission
✅ c) Asphyxiation
Explanation: High levels of CO₂ can displace oxygen and cause suffocation.
Which of these events naturally reduces atmospheric CO₂?
a) Volcanic eruption
b) Deforestation
c) Afforestation
d) Burning fossil fuels
✅ c) Afforestation
Explanation: Planting trees increases CO₂ absorption and reduces its atmospheric concentration.
What happens to limewater when excess CO₂ is passed through it?
a) It becomes clear
b) It turns red
c) It turns blue
d) It forms soap
✅ a) It becomes clear
Explanation: Excess CO₂ turns milky limewater clear again by forming soluble calcium bicarbonate.
Carbon dioxide gas is:
a) Basic
b) Acidic
c) Neutral
d) Amphoteric
✅ b) Acidic
Explanation: CO₂ forms weak carbonic acid when dissolved in water, making it mildly acidic.
Dry ice is stored in:
a) Boiling water
b) Plastic box
c) Air-tight containers
d) Open steel tray
✅ c) Air-tight containers
Explanation: Dry ice sublimates quickly; airtight containers slow down sublimation.
In blood, CO₂ is transported mainly in the form of:
a) Bicarbonate ions
b) Carbonic acid
c) CO₂ gas
d) Carbohydrates
✅ a) Bicarbonate ions
Explanation: Around 70% of CO₂ is carried as bicarbonate (HCO₃⁻) in blood plasma.
Which technique is used to capture and store CO₂ to reduce emissions?
a) Ozonation
b) Carbon trading
c) Carbon capture and storage (CCS)
d) Biogasification
✅ c) Carbon capture and storage (CCS)
Explanation: CCS traps CO₂ from power plants and stores it underground to reduce atmospheric release.
Why is CO₂ used in greenhouses?
a) To cool plants
b) To reflect sunlight
c) To increase photosynthesis
d) To filter UV rays
✅ c) To increase photosynthesis
Explanation: Higher CO₂ levels accelerate plant growth by enhancing photosynthesis.
Which of the following forms weak acid with water?
a) O₂
b) CO₂
c) H₂
d) N₂
✅ b) CO₂
Explanation: CO₂ reacts with water to form carbonic acid (H₂CO₃).
What is the effect of high CO₂ concentration in oceans?
a) Decrease in salinity
b) Alkalinity
c) Coral bleaching
d) Ocean warming
✅ c) Coral bleaching
Explanation: Ocean acidification due to CO₂ harms marine life and coral ecosystems.
What does the greenhouse effect lead to?
a) Cooling
b) Faster winds
c) Climate change
d) Ozone depletion
✅ c) Climate change
Explanation: Greenhouse gases like CO₂ trap heat, leading to global warming and climate change.
One molecule of CO₂ contains:
a) 2 carbon atoms
b) 2 oxygen atoms
c) 1 hydrogen atom
d) 3 oxygen atoms
✅ b) 2 oxygen atoms
Explanation: CO₂ = 1 carbon + 2 oxygen atoms.
CO₂ is a product of:
a) Neutralization
b) Displacement
c) Combustion
d) Photolysis
✅ c) Combustion
Explanation: Burning carbon-containing fuels in oxygen releases CO₂.