Question

Air is about 78% nitrogen gas (N2) by mass. The molar mass of nitrogen gas is 28.0 g/mol. A 100.0-g sample of air contains how many moles of nitrogen?

Answer 1

(78%×100g)/100% = 0,78×100g = 78g N₂

1 mole N₂ ------ 28g
X ----------------- 78g
X = 78/28 = 2,7857 moles

:)

Answer 2

Answer: The number of moles of nitrogen will be 3.57 moles.

Explanation:

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

$Moles=\frac{\text{Given mass}}{\text{Molar mass}}$

We are given:

Given mass of the nitrogen = 100 g

Molar mass of the sample = 28g/mol

Putting values in above equation, we get:

$\text{Moles of Nitrogen}=\frac{100g}{28g/mol}=3.57moles$

Hence, the number of moles of nitrogen will be 3.57 moles.