What is the volume of air at any given pressure ie 700kPa?

There are many formula's for calculating the volume of air. The most basic is the ideal gas law. For this law, the answer would be V = R * T / (P * MW), where R = a constant, 10.73, T is the temperature in Rankine, which is Fahrenheit + 459.7, P is the absolute pressure in PSIA, and MW is the molecular weight, in this case use 28.5. The answer will be in cubic feet per pound of air. For example, if I had a container of air and the pressure was reading 10 pounds on the gauge, and the temperature was 70, then the formula would be as follows: PSIA = PSIG + 14.7, so PSIA = 24.7. T = 70 + 459.7, so T = 529.7. V = 10.73 * 529.7 / (24.7 * 28.5). The answer is in cubic feet per pound of air. The volume would be that of its container regardless of pressure.