We are surrounded more by gas mixtures than isolated gases. The air we breathe is an example of a mixture of various gases, the main ones being nitrogen (N2), which corresponds to about 80% of the air; and oxygen (O2), which is almost 20%.
Since they are so present in our daily lives, it is necessary to analyze two important quantities when it comes to gas mixtures, which are: partial pressure and partial volume. Next, both will be explained:
1. Partial pressure of gases:
The partial pressure of a gas is the pressure it would exert if it were alone, under the same conditions of temperature and volume as the mixture.
According to Dalton, the sum of the partial pressures of the gases that form the mixture results in the total pressure (p) of the mixture. For example, if the air pressure is 1.0 atm, the partial pressure of N2 will be 0.8 (80% of the total pressure) and the partial pressure of O2 will be equal to 0.2% (20% of the total pressure of the mixture).
This Dalton's Law is also shown by the fraction in quantity of matter (X). This fraction in the case of nitrogen is given by
0.8 mol.1.0 mol
PN2= p. XN2
PN2= 1.0 atm. 0.8 = 0.8 atm.
You can also calculate each partial pressure using the gas state equation:
Equation of state of gases: PV = nRT
Determination of N partial pressure2:PN2. V = nN2 . RT
2. Partial volume of gases:
Similar to partial pressure, the partial volume corresponds to the volume that a gas occupies under the conditions of temperature and pressure of the mixture.
THEAmagat's Law says the sum of the partial volumes is equal to the total volume, as well as the pressure case seen earlier. For this reason, we use the equation of state of gases, with the only difference that now we put the partial volume of the gas and not the pressure:
P. VN2= nN2 . RT
It is also possible to calculate the partial volume of each gas component of the mixture through the fraction in quantity of matter.
By Jennifer Fogaça
Graduated in Chemistry
Source: Brazil School - https://brasilescola.uol.com.br/quimica/misturas-gasosas.htm
