Multiple Choice
Which pair of gas samples at standard temperature and pressure (STP) contains the same total number of molecules?
69
views
7. Gases
Standard Temperature and Pressure
Multiple Choice
Which of the following is NOT considered a standard state under standard temperature and pressure (STP) conditions?
A
Liquid water at 1 atm and 273.15 K
B
Carbon dioxide gas at 2 atm and 273.15 K
C
Nitrogen gas at 1 atm and 273.15 K
D
Oxygen gas at 1 atm and 273.15 K
Verified step by step guidance1
Understand the definition of standard state conditions: Standard state refers to the most stable form of a substance at 1 atm pressure and a specified temperature, usually 25°C (298.15 K), but sometimes 0°C (273.15 K) is used for STP. The key point is that the pressure must be 1 atm.
Identify the pressure and temperature conditions given for each substance in the problem. Note that standard state requires a pressure of exactly 1 atm and the given temperature (273.15 K in this case).
Check each option against the standard state criteria: Liquid water at 1 atm and 273.15 K is standard state because water is liquid at 1 atm and 273.15 K; Nitrogen gas at 1 atm and 273.15 K is standard state; Oxygen gas at 1 atm and 273.15 K is standard state.
Look at the option with carbon dioxide gas at 2 atm and 273.15 K. Since the pressure is 2 atm, which is not 1 atm, this does not meet the standard state pressure condition.
Conclude that the substance not considered in its standard state under the given conditions is carbon dioxide gas at 2 atm and 273.15 K because its pressure deviates from the required 1 atm standard state pressure.
Related Videos
Related Practice
