One mole of an ideal gas at STP (Standard conditions of Temperature and Pressure) occupies one standard molar volume. The Ideal Gas Law states: PV = nRT; since n, R are constant in this problem; rearrange the terms to equate PV/T for the two temperatures and pressures.
This relationship is useful when doing analysis of chemical composition of gasses because gas properties depend on temperature and pressure, solving for the quantities at STP becomes useful when comparing the results to different gases.
This equation is useful for solving problems of the form:
How many moles are in 3 L liters of gas at 255 K and 1 atm ?
First we solve for the Volume at STP and convert volume to moles.
Standard conditions of temperature and presuure is usually abbreviated as STP.
The Standard temperature for gases is known to be 0`""^@C` = 273.15 `K` and standard pressure , 1 bar = 100 kPa = `10^5` Pa. There is an old definition and usage where the pressure was based on 1 atm, but this usage is discouraged. The definition recommended by the International Union of Pure and Applied Chemistry (IUPAC) is:
Standard Temperature and Pressure (STP): 0`""^@C` and 1 bar = `10^5` Pa |