Question

1. How many grams of helium must be released to reduce the pressure to 69 atm assuming ideal gas behavior?

2. If the pressure exerted by ozone, O3, in the stratosphere is 3.0×10−3atm and the temperature is 251 K , how many ozone molecules are in a liter?

3. Carbon dioxide makes up approximately 0.04% of Earth's atmosphere. If you collect a 3.0 L sample from the atmosphere at sea level (1.00 atm) on a warm day (29 ∘C), how many CO2 molecules are in your sample?

Answer 1

1.
We nned to mention the initial pressure
2.
use:
P*V=n*R*T
3*10^-3*1 = n*0.0821*251
n=1.456*10^-4 mol

number of molecules = number of moles * Avogadro's number
                                              = 1.456*10^-4 mol * (6.022*10^23)
                                               = 8.8*10^19 molecules
Answer: 8.8*10^19 molecules

3.
volume of CO2 = 0.04% of 3 L = 1.2*10^-3 L
use :
P*V=n*R*T
1*(1.2*10^-3)= n*0.0821*(273+29)
n = 4.84*10^-5 mol

number of molecules = number of moles * Avogadro's number
                                              = 4.84*10^-5 * (6.022*10^23)
                                               = 2.9*10^19 molecules
Answer: 2.9*10^19 molecules