Final answer:
The pressure given off by helium in a container that holds a mixture of gases with a total of 30 atm pressure, where oxygen contributes 12 atm and nitrogen 11 atm, can be found using Dalton's law of partial pressure and is calculated to be 7 atm.
Step-by-step explanation:
The pressure of helium in a container that holds a mixture of oxygen, nitrogen, and helium can be determined by using the Dalton's law of partial pressure. According to this law, the total pressure exerted by a mixture of non-reactive gases is the sum of the partial pressures of individual gases. Given that the total pressure in the container is 30 atm, the pressure due to oxygen is 12 atm, and the pressure due to nitrogen is 11 atm, we can calculate the partial pressure of helium.
Using the formula for Dalton's law:
Ptotal = PO2 + PN2 + PHe
Where Ptotal is the total pressure, PO2 is the partial pressure of oxygen, PN2 is the partial pressure of nitrogen, and PHe is the partial pressure of helium.
PHe = Ptotal - (PO2 + PN2)
PHe = 30 atm - (12 atm + 11 atm)
PHe = 7 atm
Therefore, the pressure given off by helium in the container is 7 atm.