The average out door concentration of carbon monoxide ,co at 15 c and 1 atm of pressure is about 900 micrograms per cm^3 . What is this concentration expressed : on ppm scale ? And on the molecules /cm^3scale?
To convert the concentration of carbon monoxide from micrograms per cm^3 to parts per million (ppm) and molecules per cm^3, you'll need to use a conversion factor and the molar mass of carbon monoxide.
1. Converting to ppm:
To convert micrograms per cm^3 to ppm, you need to know the volume of 1 ppm. For gases at standard temperature and pressure (STP), 1 ppm is equivalent to 1.96 μg/L (micrograms per liter). So, we'll need to convert the volume from cm^3 to liters before converting to ppm.
Step 1: Convert cm^3 to L:
1 cm^3 = 1 mL = 0.001 L (since 1 L = 1000 cm^3)
Step 2: Convert μg/cm^3 to μg/L:
Multiply the given concentration (900 μg/cm^3) by the conversion factor 0.001 to get the concentration in μg/L.
900 μg/cm^3 * 0.001 = 0.9 μg/L
Step 3: Convert μg/L to ppm:
To convert μg/L to ppm, divide the concentration in μg/L by the conversion factor 1.96 μg/L.
0.9 μg/L / 1.96 μg/L = 0.459 ppm (approximately)
Therefore, the concentration of carbon monoxide expressed on the ppm scale is approximately 0.459 ppm.
2. Converting to molecules/cm^3:
To convert from ppm to molecules/cm^3, you need to use Avogadro's number (6.022 x 10^23 molecules/mol). We'll also need to calculate the moles of carbon monoxide at standard temperature and pressure (STP).
Step 1: Calculate the moles of carbon monoxide at STP:
To do this, we'll use the ideal gas law: PV = nRT.
At STP, the temperature (T) is 273.15 K, pressure (P) is 1 atm, and R (ideal gas constant) is 0.0821 L·atm/(mol·K).
n = (PV) / (RT)
= (1 atm * 0.001 L) / (0.0821 L·atm/(mol·K) * 273.15 K)
≈ 4.003 x 10^-5 mol
Step 2: Convert moles to molecules:
Multiply the moles of carbon monoxide by Avogadro's number to get the number of molecules.
4.003 x 10^-5 mol * 6.022 x 10^23 molecules/mol
≈ 2.408 x 10^19 molecules
Therefore, the concentration of carbon monoxide expressed on the molecules/cm^3 scale is approximately 2.408 x 10^19 molecules/cm^3.