Question

How do you find the pressure at STP and SATP?

Answer 1

There are three important conditions where experiments are carried out. These are STP, SATP, and NTP. The long form of the STP is standard temperature and pressure while SATP is standard ambient temperature and pressure and NTP is normal temperature and pressure. To find out the pressure at the STP and STAP we have to first use the ideal gas equation. Rearrange the ideal gas equation for pressure and then substitute all other values and then calculate the pressure.

Complete step by step answer:
STP and SATP are the standard conditions where experiments are carried. Here, STP is standard temperature and pressure while SATP is standard ambient temperature and pressure.
The pressure at STP and STAP is calculated by using the ideal gas equation as follows:
${\text{PV = nRT}}$
Here, we have to first rearrange the equation for pressure and then calculate the pressure.

$\Rightarrow {\text{P = }}\dfrac{{{\text{nRT}}}}{{\text{V}}}$
At STP temperature is ${0^\circ }{\text{C}}$ that is $273.15\,{\text{K}}$, and volume is $22.4\,{\text{L}}\,$, the gas constant is ${\text{0}}{\text{.08205L}}\,{\text{bar}}\,{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}$, there is one mole of gas.

$\Rightarrow {\text{P = }}\dfrac{{{\text{nRT}}}}{{\text{V}}}$
$\Rightarrow {\text{P = }}\dfrac{{{\text{1}}\,{\text{mol}} \times {\text{0}}{\text{.08205L}}\,{\text{bar}}\,{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}} \times 273.15\,{\text{K}}}}{{22.4\,{\text{L}}\,}}$
$\Rightarrow {\text{P = }}1.000\,{\text{bar}}$
Thus, pressure at STP is $1.000\,{\text{bar}}$.

At SATP temperature is ${25^\circ }{\text{C}}$ that is $298.15\,{\text{K}}$, and volume is $24.789\,{\text{L}}\,$, the gas constant is ${\text{0}}{\text{.08205L}}\,{\text{bar}}\,{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}}$, there is one mole of gas.
$\Rightarrow {\text{P = }}\dfrac{{{\text{nRT}}}}{{\text{V}}}$
$\Rightarrow {\text{P = }}\dfrac{{{\text{1}}\,{\text{mol}} \times {\text{0}}{\text{.08205L}}\,{\text{bar}}\,{{\text{K}}^{ - 1}}{\text{mo}}{{\text{l}}^{ - 1}} \times 298.15\,{\text{K}}}}{{24.789\,{\text{L}}\,}}$
$\Rightarrow {\text{P = }}0.9869\,{\text{bar}}$
$\Rightarrow {\text{P}} \cong 1.00\,{\text{bar}}$
Thus, pressure at SATP is $1.000\,{\text{bar}}$.

Note: The pressure is nothing but the force applied to the unit area of an object. If force has unit Newton and the area is in meters then the unit of the pressure is Newton per meter. The pressure is also expressed in units of Pascal, torr, mmHg, etc. The ideal gas equation relates pressure, volume, temperature, numbers of moles of gas, and the gas constant as follows: ${\text{PV = nRT}}$