Answer:
a)  No molecules of hydrogen
b) four molecules of ammonia
c) four left molecules of nitrogen.
Explanation:
The balanced reaction between nitrogen and hydrogen molecules to give ammonia molecules is:

Thus one molecule of nitrogen will react with three molecules of hydrogen to give two molecules of ammonia.
We have six molecules of each nitrogen and hydrogen in the closed container and they undergo complete reaction it means the limiting reagent is hydrogen. For six molecules of nitrogen, eighteen molecules of hydrogen will be required. 
So six molecules of hydrogen will react with two molecules of nitrogen to give four molecules of ammonia.
The product mixture will have
a) No molecules of hydrogen
b) four molecules of ammonia
c) four left molecules of nitrogen.
 
        
             
        
        
        
Water moved through the water cycle by changing its state. Think, for example, of water evaporating (liquid to gas), snow sublimating (solid to gas) or melting (solid to liquid), rain (gas to liquid), sleet (liquid to solid), or snow (gas to solid).
The answer would thus be A.
        
                    
             
        
        
        
This movement is known as convection or convection currents. This occurs due to the fact that warmer fluid is of lower density than colder fluid. This causes warmer fluid to rise and colder fluid to sink. This creates circulatory currents within the body of the fluid.
        
             
        
        
        
Atomic Number is the same as the number of protons in an element.
Mass Number is the number of Protons + Neutrons in an element.
Atomic Number: 6 means 6 Protons
Mass Number: 15 means 15 atoms that are a proton/neutron.
We are given out of the 15 atoms, 6 of them are protons, so the other 9 must be Neutrons.
15 - 6 = 9 so there must be 9 Neutrons.
There are 9 Neutrons in atom's nucleus.
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