Question

Ammonia is produced by the following reaction.


3H2(g) + N2(g) --------> 2NH3(g)


When 7.00 g of hydrogen react with 70.0 g of nitrogen, hydrogen is considered the limiting reactant because
7.5 mol of hydrogen would be needed to consume the available nitrogen.
7.5 mol of nitrogen would be needed to consume the available hydrogen.
hydrogen would produce 7.5 mol more ammonia than nitrogen.
nitrogen would produce 7.5 mol more ammonia than hydrogen.

Answer 1

I believe the correct answer from the choices listed above is the first option. When 7.00 g of hydrogen react with 70.0 g of nitrogen, hydrogen is considered the limiting reactant because 7.5 mol of hydrogen would be needed to consume the available nitrogen. The limiting reactant is the reactant which would be consumed first in the reaction. Hope this answers the question. 

Answer 2

Answer: The correct statement is 7.5 mol of hydrogen would be needed to consume the available nitrogen.

Explanation:

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

$\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}$

• For Hydrogen:

Given mass = 7 grams

Molar mass = 2 g/mol

Putting values in above equation:

$\text{Moles of hydrogen}=\frac{7g}{2g/mol}=3.5mol$

• For Nitrogen:

Given mass = 70 grams

Molar mass = 28 g/mol

Putting values in above equation:

$\text{Moles of nitrogen}=\frac{70g}{28g/mol}=2.5mol$

• For the given chemical reaction:

$3H_2(g)+N_2(g)\rightarrow 2NH_3(g)$

By Stoichiometry of the reaction:

1 mole of nitrogen is consumed by 3 moles of hydrogen

2.5 moles of nitrogen is consumed by = $\frac{3}{1}\times 2.5=7.5mol$ of nitrogen gas.

Hydrogen is considered as a limiting reagent because it limits the formation of products and will be totally consumed by a less quantity of excess reagent.

Hence, the correct statement is 7.5 mol of hydrogen would be needed to consume the available nitrogen.