Air is composed of about 21% oxygen, 78% nitrogen and 1% other gases. What is the partial pressure of oxygen at STP?
I'd say 21% of the standard pressure, and you know what that is.
To determine the partial pressure of oxygen (O2) at standard temperature and pressure (STP), we'll need to use the ideal gas law. The ideal gas law equation is:
PV = nRT
Where:
P represents pressure
V represents volume
n represents the number of moles
R is the ideal gas constant
T represents temperature
At STP, the pressure (P) is 1 atmosphere (atm) and the temperature (T) is 273.15 Kelvin (K). We know that the air is composed of approximately 21% oxygen. Therefore, the moles of oxygen can be calculated as follows:
(21/100) * 1 mole = 0.21 moles (approx.)
Now we can substitute the known values into the ideal gas law equation and solve for the partial pressure of oxygen (P):
P * V = (0.21 moles) * (0.0821 L*atm/mol*K) * (273.15 K)
Simplifying the equation:
P * V = 5.66042315 L*atm
Since we're looking for the partial pressure of oxygen (P), we need to find the value of V. At STP, 1 mole of any gas occupies 22.4 liters (L). Since the percentage composition of oxygen is given by volume, we can assume the volume of air to be 100 L, hence the volume of oxygen (V) would be:
V = (0.21 moles O2) * (22.4 L/mol)
V = 4.704 L (approx.)
Substituting the volume (V) into the equation:
P * 4.704 L = 5.66042315 L*atm
Solving for P:
P = 5.66042315 L*atm / 4.704 L
P = 1.20316227 atm
Therefore, the partial pressure of oxygen at STP is approximately 1.20 atmospheres.
To find the partial pressure of oxygen at STP (Standard Temperature and Pressure), we need to know the total pressure of the air at STP.
At STP, the total pressure is defined as 1 atmosphere or 101.325 kilopascals (kPa).
Since oxygen constitutes about 21% of the air, we can calculate its partial pressure using the following formula:
Partial Pressure of Oxygen = Total Pressure * Fraction of Oxygen
Plugging in the values:
Partial Pressure of Oxygen = 101.325 kPa * 0.21
Partial Pressure of Oxygen ≈ 21.28 kPa
Therefore, at STP, the partial pressure of oxygen in air is approximately 21.28 kilopascals.