Question #af461

1 Answer
Jul 21, 2015

Answer:

They are a set of conditions for pressure and temperature.

Explanation:

I assume that you want to know the difference between STP and NTP.

Both STP and NTP are a set of conditions that establish working temperature and pressure.

STP, or Standard Temperature and Pressure, conditions correspond to a temperature of #0^@"C"#, or 273.15 K, and a pressure of 100 kPa.

NTP, or Normal Temperature and Pressure, conditions correspond to a temperature of #20^@"C"#, or 293.15 K, and a pressure of 1 atm.

A pressure of 1 atm is equivalent to 101.325 kPa.

This means that these two sets of conditions differ by

  • Temperature - STP is #0^@"C"# and NTP is #20^@"C"#
  • Pressure - STP is 100 kPa and NTP is 101.325 kPa

When it comes to idel gases, these two conditions also differ in the volume occupies by 1 mole of gas - this is called the molar volume of a gas.

To show why that is, use the ideal gas law equation

  • At STP conditions

#PV = nRT => V/n = (RT)/P#

#V/n = (0.082 (cancel("atm") * "L")/("mol" * cancel("K")) * (273.15 + 0)cancel("K"))/(100/101.325cancel("atm")) = color(green)("22.7 L/mol")#

This tells you that 1 mole of any ideal gas will occupy exactly

#1cancel("mole") * "22.7 L"/cancel("mol") = "22.7 L"#

  • At NTP conditions

#V/n = (0.082 (cancel("atm") * "L")/("mol" * cancel("K")) * (273.15 + 20)cancel("K"))/(101.325/101.325cancel("atm")) = color(green)("24.0 L/mol")#

This time, 1 mole of any ideal gas will occupy

#1cancel("mole") * "24.0 L"/cancel("mol") = "24.0 L"#