Question

What conditions are considered "standard temperature and pressure" (STP) for gases? Suggest a reason why these particular conditions might have been chosen for STP.

Short answer

Standard Temperature and Pressure (STP) are defined by the International Union of Pure and Applied Chemistry (IUPAC) as a temperature of \(273.15 K\) (0°C or 32°F) and a pressure of \(100 kPa\) (1 atm or 14.7 psi). These conditions might have been chosen because they represent average natural conditions: 0°C is the midpoint between the freezing and boiling points of water, and 1 atm is the average sea-level atmospheric pressure on Earth. These conditions are easily reproducible, provide a convenient reference point for comparing different gases, and simplify calculations since many common gases behave ideally at this temperature.

Step-by-step solution

Definition of Standard Temperature and Pressure (STP)

Standard Temperature and Pressure (STP) are defined as the set of conditions for which gases are generally measured. The International Union of Pure and Applied Chemistry (IUPAC) defines STP conditions as a temperature of \(273.15 K\) (0°C or 32°F) and a pressure of \(100 kPa\) (1 atm or 14.7 psi).

Reason for Choosing STP Conditions

The reason for choosing these specific conditions as the standard temperature and pressure might be because these are the average conditions found in nature. 0°C is the midpoint between the freezing and boiling points of water, and 1 atm is the average sea-level atmospheric pressure on Earth. As a result, these conditions are easily reproducible in laboratories, and they provide a convenient reference point for comparing the properties of different gases. Another reason is that working with gases at 0°C makes calculations simpler since many common gases behave ideally at this temperature.