Question

What is the limiting reactant when 1.50 g of lithium and 1.50 g of nitrogen combine to form lithium nitride, a component of advanced batteries, according to the following unbalanced equation? Li + N2 ⟶ Li3 N

Answer 1

Answer: The limiting reagent in the given equation is lithium metal.

Explanation:

Limiting reagent is defined as the reagent which is present in less amount and also it limits the formation of products.

Excess reagent is defined as the reagent which is present in large amount.

To calculate the number of moles, we use the equation:

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$   ....(1)

• For Lithium metal:

Given mass of lithium metal = 1.50 g

Molar mass of lithium metal = 6.94 g/mol

Putting values in equation 1, we get:  

$\text{Moles of lithium metal}=\frac{1.50g}{6.94g/mol}=0.216mol$

• For nitrogen gas:

Given mass of nitrogen gas = 1.50 g

Molar mass of nitrogen gas = 28.01 g/mol

Putting values in equation 1, we get:  

$\text{Moles of nitrogen gas}=\frac{1.50g}{28.01g/mol}=0.053mol$

• For the given chemical reaction:

$6Li+N_2\rightarrow 2Li_3N$

By stoichiometry of the reaction:

6 moles of lithium reacts with 1 mole of nitrogen gas

So, 0.216 moles of lithium will react with = $\frac{1}{6}\times 0.216=0.036moles$ of nitrogen gas.

As, the given amount of nitrogen gas is more than the required amount. Thus, it is considered as an excess reagent.

So, lithium metal is considered as a limiting reagent because it limits the formation of products.