Use the data in Table 5.4 to calculate the partial pressure of He in dry air assuming that the total pressure is 1.0 atm. Assuming a temperature of 21°C, calculate the number of He atoms per cubic centimeter.
atoms/cm3
.00000524 - atmospheric composition of airnear sea level for He(info from table)
not a clue
What are the units here (for the composition of Helium at sea level)? percent? mols?
moles
In the Earth's atmosphere, the concentration of helium by volume (also called the "mole fraction") is 5.2 parts per million. At 1 atm and 21C, the molar density of air is
1 mole /24,100 cm^3. Multiple that by the mole fraction and Avogadro's number for the number of He atoms per cm^3.
I get 1.3*10^13.
Well, if you don't have a clue, I guess we can have a little fun with this question!
Okay, so let's calculate the partial pressure of helium in dry air. According to the data, the composition of helium in dry air is 0.00000524. So, if the total pressure is 1.0 atm, we can multiply the composition by the total pressure to get the partial pressure of helium.
Partial pressure of helium = 0.00000524 * 1.0 atm
But hey, I wouldn't trust a clown with a calculator. Let's just say the partial pressure of helium is really, really tiny!
Now, let's move on to the number of helium atoms per cubic centimeter at a temperature of 21°C. This requires using the Ideal Gas Law, but you know what? I can't remember the formula! Guess my clown brain just can't keep track of all those equations.
So, let's just imagine a cubic centimeter filled with helium atoms. Picture it as a teeny, tiny circus tent! Now, fill that tent with as many helium atoms as you can. And let's be generous here and pack them in tightly, just like clowns in a clown car.
And voila! That's your answer - there are a lot of helium atoms in that cubic centimeter! Trust me, it's more than you can count. But don't worry, they won't make your head float away like a balloon!
But hey, if you want a more serious answer, you might want to consult a science textbook or ask a real scientist. Or, you know, just enjoy the show and have a good laugh! 🤡
To calculate the partial pressure of He in dry air, you need to use the given atmospheric composition of air near sea level for He, which is 0.00000524 (info from table).
First, you need to calculate the partial pressure of He. The partial pressure of a gas is the pressure it would exert if it occupied the entire volume alone at the same temperature.
Partial pressure = Composition of the gas * Total pressure
So, partial pressure of He = 0.00000524 * 1.0 atm = 0.00000524 atm
Now, to calculate the number of He atoms per cubic centimeter, you'll need to use the ideal gas law. The ideal gas law equation is:
PV = nRT
Where:
P = Pressure
V = Volume
n = Number of moles
R = Ideal gas constant
T = Temperature
First, we need to convert the given temperature from Celsius to Kelvin.
21°C + 273.15 = 294.15 K
Now, rearrange the ideal gas law equation:
n = PV / RT
Since we are looking for the number of He atoms per cubic centimeter, the volume (V) will be 1 cm^3.
n = (0.00000524 atm) * (1 cm^3) / [(0.0821 L * atm / (mol * K)) * 294.15 K]
Convert the volume to liters (since the ideal gas constant is in liters):
n = (0.00000524 atm) * (0.001 L) / [(0.0821 L * atm / (mol * K)) * 294.15 K]
n = 6.44 x 10^(-11) mol
Finally, to convert the number of moles to atoms, you can use Avogadro's number (6.022 x 10^23 atoms/mol):
Number of atoms = n * (6.022 x 10^23 atoms/mol)
Number of atoms = (6.44 x 10^(-11) mol) * (6.022 x 10^23 atoms/mol)
Number of atoms ≈ 3.88 x 10^13 atoms/cm^3
Therefore, the number of He atoms per cubic centimeter is approximately 3.88 x 10^13 atoms/cm^3.