Normal Temperature and Pressure (NTP)

09th Apr 2019 @ 3 min read

Normal Temperature and Pressure defined by NIST

Normal temperature is 20 ℃ or 293.15 K or 68 ℉.

Normal pressure is 1 atm or 101.325 kPa or 760 mmHg (or torr) or 14.6959 psi.

Why do we need NTP

NTP is introduced by the National Institute of Standards and Technology (NIST). Normal temperature as per NTP is 20 ℃. This temperature is a more realistic and convenient condition in the world compared to 0 ℃ which is the standard temperature of STP. NTP is widely used as a more practical standard by various industries throughout the world.

Volume at NTP

The volume of gases is usually calculated at Normal temperature and pressure. The molar volume V_m of an ideal gas is defined as:

$V_m = \frac{RT}{P}$

where R is the ideal gas constant, its value is 8.314 J K⁻¹ mole⁻¹.

At NTP,

$V_\text{m}=\frac{RT}{P} &= \frac{8.314 \times 293.15}{101\,325} \\ &=0.02405 \,\text{m}^3\,\text{mol}^{-1} \\&=24.05 \, \text{dm}^3 \,\text{mol}^{-1}$

With the help of molar volume, we can also calculate the density of air at NTP.