Question

A sample of fluorine gas has a volume of 5.63 L at 14°C and standard pressure. What will be the pressure in atm if the moles of gas and the temperature do not change but the volume is expanded to 9.21 L?
I know that to solve this, it's (pressure x 5.63L) / 9.21L. Temperature and moles are constant so we can ignore those. But I don't know what's the standard pressure or what it even means

Answer 1

With standard pressure there is a set list of values. (at STP), most common is 760torr. So whenever you see "at STP" or "at standard temperature pressure" you will use 760torr for pressure. Same thing goes with temperature, if you're not given temp and it says at STP you will use 273K.

For this problem:

You will be using the combined gas law:

(Pressure 1) x (Volume 1) / (Temp. 1) = (Pressure 2) x (Volume 2) / (Temp. 2)

(760torr) x (5.63L) / (287K) = (?) (9.21L) / (287K)

Pressure 2 = 465torr

*Hope this clarifies STP for you! :)