A balloon vendor at a street fair is using a tank of helium to fill her balloons. The tank has a volume of 113.0 L and a pressure of 122.0 atm at 25.0 °C. After a while, she notices that the valve has not been closed properly. The pressure had dropped to 112.0 atm (The tank is still at 25.0 °C).

Given dа ta:

P₁ = 122 atm

P₂ = 112 atm

V₁ = 113 L

V₂ = ?

Solution:

Let suppose the gas is acting ideally. According to Ideal gas equation, keeping the temperature constant,

P₁ V₁ = P₂ V₂

Solving for V₂,

V₂ = P₁ V₁ / P₂

Putting Values,

V₂ = (122 atm * 113 L) : 112 atm

V₂ = 113 L

Converting Volume to Moles,

As,

22.4 L is occupied by = 1 mole of He gas

So,

113 L will occupy = X moles of He gas

Solving for X,

X = (113 L * 1 mole) : 22.4 L

X = 5.04 Moles of He