General Science Class 6th MCQs=745

• Air is necessary for breathing and burning.              
• Air is necessary for respiration.
• Air is a mixture of many colorless gasses.
  
• The surface of earth is surrounded by a thick layer of air (Gases), which reaches a height about 400km.
  
• Air consists of 78% nitrogen, 21% oxygen, 0.03% carbon dioxide and 1% other gasses.
• Nitrogen is colorless and odorless gas.
• It is used in normal growth and development of plants.
  
• Liquid nitrogen is used as a coolant.
  
• Animals use Nitrogen in the form of proteins.
• Plants use Nitrogen in the form of nitrates (Fertilizer).
• Oxygen is colorless and odorless gas.
• Liquid oxygen is used as fuel in space ship.
• Oxyacetylene flame is used in cutting and welding of metals.
• Oxygen is essential for breathing.
  
• Carbon dioxide gas is heavier than air and fairly soluble in water.
• Carbon dioxide is used in fire extinguishers.
• Gaseous carbon dioxide upon cooling (to -78.5⁰C) directly becomes a solid and is known as dry ice.
• Carbon dioxide also used to prepare urea fertilizers.
• Noble gases are inactive, so they are also called inert gases.
• Argon is used for filling the electric bulbs.
• Helium and hydrogen gases are used for filling balloons.
  
• Neon signs are used for advertising boards.

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Which of these gases are present in maximum amount in air………………
a) Oxygen                   
b) Nitrogen    
c) Chlorine                  
d) Carbon dioxide

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Oxygen is not necessary for?
a) Combustion            
b) rusting        
c) Respiration             
d) Photosynthesis

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Carbon dioxide is used in?
a) Soft Drink               
b) Fire extinguishers   
c) Photosynthesis        
d) all of these

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Which is true for nitrogen?
a) used as a dry ice     
b) used as a coolant
c) used in respiration  
d) used in combustion

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What is the volume of oxygen and carbon dioxide in air?
a) 21 % carbon dioxide and 0.03 % oxygen
b) 0.03 % carbon dioxide and 78 % oxygen
c) 78 % carbon dioxide and 21 % oxygen
d) 0.03 % carbon dioxide and 21 % oxygen

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