2. A sample of neon gas has a volume of 87.6 L at STP. How many moles are present?

3.91 moles of Neon

Explanation:

According to Avogadro's Law, same volume of any gas at standard temperature (273.15 K or O °C) and pressure (1 atm) will occupy same volume. And one mole of any Ideal gas occupies 22.4 dm³ (1 dm³ = 1 L).

Data Given:

n = moles = ?

V = Volume = 87.6 L

Solution:

As 22.4 L volume is occupied by one mole of gas then the 16.8 L of this gas will contain ...

= (1 mole * 87.6 L) : 22.4 L

= 3.91 moles

2nd Method:

Assuming that the gas is acting ideally, hence, applying ideal gas equation.

P V = n R T ∴ R = 0.08205 L⋅atm⋅K⁻¹⋅mol⁻¹

Solving for n,

n = P V / R T

Putting values,

n = (1 atm * 87.6 L) / (0.08205 L⋅atm⋅K⁻¹⋅mol⁻¹ * 273.15K)

n = 3.91 moles

Result:

87.6 L of Neon gas will contain 3.91 moles at standard temperature and pressure.