1. Understand STP
STP stands for Standard Temperature and Pressure:
* Temperature: 0°C (273.15 K)
* Pressure: 1 atm (101.325 kPa)
2. Ideal Gas Law
We can use the ideal gas law to relate the density of a gas to its molar mass and other conditions:
* PV = nRT
* P = Pressure (atm)
* V = Volume (L)
* n = Number of moles
* R = Ideal gas constant (0.0821 L·atm/mol·K)
* T = Temperature (K)
3. Rearrange for Density
Density (ρ) is mass (m) per unit volume (V):
* ρ = m/V
We can rewrite the ideal gas law to solve for density:
* ρ = (n * M) / V
* M = Molar mass of the gas (g/mol)
Substituting the ideal gas law (PV = nRT) for 'n' in the density equation:
* ρ = (PM) / (RT)
4. Calculate the Density of Bromine Vapor
* Molar Mass of Bromine (Br₂): 79.904 g/mol * 2 = 159.808 g/mol
* Pressure (P): 1 atm
* Temperature (T): 273.15 K
* Ideal gas constant (R): 0.0821 L·atm/mol·K
Substitute the values into the equation:
* ρ = (1 atm * 159.808 g/mol) / (0.0821 L·atm/mol·K * 273.15 K)
* ρ ≈ 7.14 g/L
Therefore, the density of bromine vapor at STP is approximately 7.14 g/L.
