In order to balance this equation you need to count each element and how many of the individual elements are in the equation. 
_H2+N2=2 NH3 
You multiply the 2 (Which is the coefficient) by the 3 (which is the subscript) This would equal 6 which indicated there are 6 hydrogen atoms on the right side so the left side should also have 6 hydrogen atoms
The missing coefficient on the left side must multiple the 2 to become 6 hydrogen 
Answer=3
        
                    
             
        
        
        
B steam causes wheels to turn is correct
        
             
        
        
        
The acronym is RNA. Ribo Nucleic Acid
        
             
        
        
        
Answer:
moles of carbon dioxide produced are 410.9 mol.
Explanation:
Given data:
Mass of C₆H₁₄O₂ = 16.5 g
Moles of O₂ = 499 mol
Moles of CO₂ = ?
First of all we will write the balance chemical equation.
2C₆H₁₄O₂  +  17O₂  →   14CO₂  +  12H₂O
moles of C₆H₁₄O₂  = mass × molar mass
moles of C₆H₁₄O₂ =  16.5 g × 118 g/mol
moles of C₆H₁₄O₂ = 1947 mol
Now we compare the moles of CO₂ with moles of O₂ and C₆H₁₄O₂ from balance chemical equation.
                  O₂      :     CO₂
                  17       :      14
                 499     :      14/17× 499 = 410.9 moles
           C₆H₁₄O₂   :   CO₂
                     2    :      14
                  1947 :     14/2× 1947 =  13629 moles
Oxygen will be limiting reactant so moles of carbon dioxide produced are 410.9 mol.
 
        
                    
             
        
        
        
Im no sure what it is i just love helping little boys out. at this age it gives me a thrill.