Answer:
CO2
Explanation:
CO2 or carbon dioxide is produced when iron is extracted from its ore. Carbon monoxide Co is used as reducing agent in iron extraction. In this reaction iron ore is reduced to iron and CO is oxidized to CO2 or carbon dioxide which is released in the process. There extraction of iron is redox reaction.
 
        
             
        
        
        
The pressure of the gas used in the weather balloon increases to expand the balloon.
Explanation:
- Weather balloons contain the boxes where the weather measurement instruments are present that is attached to the large balloon.
- Weather balloon uses gases like Hydrogen or Helium. When the weather balloon rises to the atmosphere, the air pressure decreases. This leads to the increase in the pressure of hydrogen or Helium gas used in the weather balloon. This expands the balloon.
- The gas particles hits the balloon container and generates the pressure. The increase of pressure thus helps the weather balloon to move in a constant speed through the atmosphere.
 
        
             
        
        
        
Answer:
C. NaHCO3 → Na2CO3 + H2O + CO2
Explanation:
» For a balanced equation, the number of atoms of reactants and products must be equal.
» In equation C, the reactant side has one sodium atom while ptoduct side has 2 sodium atoms.
» The balanced equations mus be;

 
        
                    
             
        
        
        
Answer:
This is heating limestone 
Explanation:
Process:
limestone is heated strongly. After a while, the limestone begins to go cloudy. Test tube is heated too much that it is beginning to  soften it. After removing limewater, test tube cools down, the pressure in the test tube drops and air pressure pushes the cold the liquid into the hot test tube with terrible result.
Products:
Limestone is also known as calcium carbonate and Limewater
Click on the link provided to show the video
https://youtu.be/RLL5rT_DeKc
or search heating calcium carbonate 
you will find a video