Question

If 125.0g of nitrogen is reacted with 125.0g of hydrogen, what is the theoretical yield of the reaction? What is the excess reactant? What is the limiting reactant? Show your work.

Answer 1

The theoretical yield of the reaction : 151.64 g

The limiting reactant :  N₂

The excess reactant : H₂

Further explanation

Reaction

N₂+3H₂⇒2NH₃

A method that can be used to find limiting reactants is to divide the number of moles of known substances by their respective coefficients(mol ratio), and the smaller become a limiting reactant

mass of N₂=125 g

mol N₂(MW=28 g/mol) :

$\tt mol=\dfrac{mass}{MW}\\\\mol=\dfrac{125}{28}=4.46$

mass H₂ = 125 g

mol H₂(MW= 2 g/mol) :

$\tt mol=\dfrac{125}{2}=62.5$

From the equation, mol ratio N₂ : H₂ = 1 : 3

Limiting reactant : N₂ : H₂ =

$\tt \dfrac{4.46}{1}\div \dfrac{62.5}{3}=4.46\div 20.8$

N₂  : limiting reactant

H₂ : excess reactant

mol NH₃ based on limiting(N₂) (from equation N₂ : NH₃ = 1 : 2)

$\tt mol~NH_3=\dfrac{2}{1}\times 4.46=8.92$

mass NH₃ (MW=17 g/mol) :

$\tt mass=mol\times MW\\\\mass=8.92\times 17=151.64$