Chemistry Help Please

Question

A very flexible helium-filled balloon is released from the ground into the air at 20.0 ºC. The initial volume of the balloon is 7.34 L, and the pressure is 760. mmHg. The balloon ascends to an altitude of 20 km, where the pressure is 42.8 mmHg and the temperature is −67.6ºC. What is the new volume of the balloon in liters, assuming it doesn't break or leak? Report your answer to the hundredths of a L without units.

Answer 1

Notice that you are given the 3 variables used to describe a gas: pressure, volume and temperature. This should immediately suggest to you to use the combined gas law that relates these three variables:

(P₁V₁)/T₁ = constant, or (P₁V₁)/T₁ =(P₂V₂)/T₂

You are given initial conditions: P1 = 760 mm Hg , V1 = 7.34 L, T1 = 20.0 deg C. You always need to convert temperature to kelvins when doing gas calculations, so add 273.15 K to 20.0 to get 293.15 K as the initial temperature.

Final conditions: P2 = 42.8 mm Hg and T2 = 273.15 + (-67.6) = 205.6 K , V2 = unknown.

It is a simple matter to plug these numbers into the equation above. Go ahead and try it yourself , and you will get the answer.