Question

21. Consider the following chemical reaction: N2+ O2 2 NO If 10.0 g of N2 reacts with excess oxygen then how many grams of NO can be formed? A) 10.7 g B) 21.4 g C) 32.9 g D) 42.8 g Page 4 of 8

Answer 1

Answer: The correct answer is Option B.

Explanation:

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

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

• For $N_2$:

Given mass of nitrogen gas = 10 g

Molar mass of nitrogen gas = 28 g/mol

Putting values in above equation, we get:

$\text{Moles of iron oxide}=\frac{10g}{28g/mol}=0.357mol$

The given chemical reaction follows:

$N_2+O_2\rightarrow 2NO$

As, oxygen gas is present in excess. Thus, it is considered as an excess reagent and nitrogen is considered as a limiting reagent because it limits the formation of products.

By Stoichiometry of the reaction:

1 mole of nitrogen gas produces 2 moles of nitrogen oxide.

So, 0.357 moles of nitrogen gas will produce = $\frac{2}{1}\times 0.357=0.714mol$ of nitrogen oxide.

Now, calculating mass of nitrogen oxide by putting values in equation 1, we get:

Moles of nitrogen oxide = 0.714 mol

Molar mass of nitrogen oxide = 30 g/mol

Putting values in equation 1, we get:

$0.714mol=\frac{\text{Mass of nitrogen oxide}}{30g/mol}\\\\\text{Mass of nitrogen oxide}=21.4g$

Hence, the correct answer is Option B.