How to calculate pressure (PSI) of a gas in a tank

[dieferbiefer]

Hello, i don't know if this is the right place to post this question but I am sure someone here can help me out. i need to be able to calculate the psi of a gas in a tank, for example let's say i have 3000 liters of hydrogen in a 1 gallon tank, what would the psi be in the tank? the only help i can find on google is that psi=f/a but that doesn't really help me.

also, i need to be able to calculate how long the gas would flow at a given psi and rate. for example, if a had a 1 gallon tank of hydrogen at 300 psi and it was being released at the rate of 20 liters/min how long would the tank of hydrogen last?

any help is much appreciated, thank you.

 

[Ainul Hassan]

For your 1st question : You need to Find a suitable value of specific volume of hydrogen regardless of corresponding pressure that fills the required volume of yours (i.e 3000 Liters).