In order to calculate the mass of nitrogen, we must first calculate the mass percentage of nitrogen in potassium nitrate. This is:
% nitrogen = mass of nitrogen / mass of potassium nitrate
% nitrogen = 14 / 101.1 x 100
The mass of nitrogen = % nitrogen x sample mass
= (14 / 101.1) x 101.1
= 14 grams
The molar weight of nitrogen is 14. Each mole of urea contains two moles of nitrogen. Therefore, for there to be 14 grams of nitrogen, there must be 0.5 moles of urea.
Mass of urea = moles urea x molecular weight urea
Mass of urea = 0.5 x 66.06
Mass of urea = 33.03 grams
        
             
        
        
        
Just as a dozen is 12 of something, a mole is about 6.02 * 10^23 of something .
        
             
        
        
        
Answer:
Moles of Hydrogen produced is 5 moles
Explanation:
The balanced Chemical equation for reaction between zinc and sulfuric acid is :

This equation tells that ; when  1 mole of Zn react with 1 mole of sulfuric acid, it produces 1 mole of zinc sulfate and 1 mole of hydrogen.
Since sulfuric acid is in excess so Zinc is the limiting reagent
(Limiting reagent : Substance which get consumed when the reaction completes, limiting reagent helps in predicting the amount of products formed) 
Limiting reagent (Zn) will decide the amount of Hydrogen produced 


So,

Hence moles of Hydrogen produced is 5 moles
 
        
             
        
        
        
Answer:
The answer to your question is D.
Explanation:
The latitudes near the equator receives the most direct solar energy.
Hope this helps :)
 
        
             
        
        
        
There's a slight error in your equation. I think you were trying to present it like this:
2C8H18 + 25O2 -> 16CO2 + 18H2O
Mole Ratio
O2 : H20
25 : 18
? moles : 18 moles
(18/18)×25 : 18 moles
25 moles : 18 moles
Final answer would be 25 moles of O2. :)
If you have any doubts that you want to clarify with me, please ask me! :) 
I will do my utmost best to help you.