A tank holding 72.4 moles of helium gas at 42.0 °C has a pressure of 1.0526 atm. How big is the tank in liters?

Question

I am struggling with Gas Laws, I don't understand it. can some one help me solve this problem?

Answer 1

A good approximation to the behavior of a gas is the Ideal gas equation. Where P is pressure, V is volume, n is moles gas, T is temperature and R is the Ideal gas constant.

 

PV = nRT

 

There are several values for R in different units you can look up. Otherwise convert the units of V, T and P to R. Here, I'll use: R = 0.0821 liter·atm/mol·K

Then convert Celsius to Kelvin (42ºC + 273.15 = 315.15 K) to match R.

 

(1.0526 atm)V = (72.4 moles He)(0.0821 L·atm/mol·K)(315.15 K)

 

V = (72.4 moles He)(0.0821 L·atm/mol·K)(315.15 K)/(1.0526 atm)

 

Units cancel out giving

V = 1779.65 L

Answer 2

PV=naRT

 

V= nRT/P

  = 72.4*8.3145*40/1.0526

 = 22875.538666666

 

But.... Does the temperature need to be in Kelvin scale? If so, then replace the 40 in the above calculation with 315 and you get 82121.55

 

Kelvin= Celsius +273