Chemistry Question

Question

How many molecules (not moles) of NH3 are produced from 8.52×10−4 g of H2?

Answer 1

Hello Kal

 

NH₃ is formed between the reaction of nitrogen and hydrogen gas.  The balanced chemical reaction is:

 

N₂ (g) + 3H₂ (g) → 2NH₃ (g)

 

Since we are starting with 8.52×10^-4 g of H₂, we need to first calculate the moles of NH₃ formed using stoichiometry,  For this calculation, we need the molar mass of H₂, which = 2 g/mol and the mole ratio of H₂ to NH₃ from the balanced reaction, which is 3:2.

 

8.52×10^-4 g H₂ x (1 mol H₂ / 2 g H₂) x (2 mol NH₃ / 3 mol H₂) = 2.84 × 10^-4 mol NH₃

 

To determine the # of molecules, we need to use avogadro's #, which states that

 

1 mole = 6.02 x 10²³ molecules

 

2.84 × 10^-4 mol NH₃ x (6.02 x 10²³ molecules NH₃ / 1 mol NH₃) = 1.71 x 10²⁰ molecules NH₃

Answer 2

Here is a step by step procedure:

 

(1)  Divide the given mass of H₂ by the molecular weight of H₂.  That gives the number of moles of H₂. 

 

(2)  Multiply the number of moles of H₂ by Avogadro's number (6.02 x 10²³).  That gives the number of molecules of H₂.

 

(3)  Multiply the number of molecules of H₂ by 2.  That gives the number of atoms of H.

 

(4)  Since there are 3 atoms of H in each NH₃ molecule, divide the number of atoms of H by 3.  That gives the maximum possible number of NH₃ molecules that can be formed. 

 

You take it from here and do the math.