Three gases, xenon, helium, and hydrogen are confined in a 10.0 L vessel at a pressure of 7.0 atm. Intially the vessel contains 3.0 moles of xenon, 2.0 moles of helium, and 2.0 moles of hydrogen. What would the partial pressure of helium be if 5.0 moles of hydrogen are added to the vessel? Assume that the volume and temperature of the vessel remain constant how do i start this? and how does it still equal 7atm if there are now 5 hydrogen? do i need to even worry about the hydrogen?
The question asks only about pressure He and Dalton gave the answer many years ago. Dalton said that the partial pressure of a gas in a mixture of gases is independent of the other gases in the mixture. So the answer to the last question you have is that you don't need to worry about H2. You didn't change anything about He or Xe; therefore, the partial pressure of He (and Xe) is the same after adding H2 as it was before adding H2. The total pressure WILL change, it won't stay 7 atm because you add additional moles H2.
PV = nRT will give you T at the beginning. You can add the moles extra H2 and recalculate pressure and the total pressure will be greater than 7 atm. The pressure of H2 will change because more moles are present but the pressure of the other gases will not change.
To solve this problem, we can use the ideal gas law equation:
PV = nRT
where P is the pressure, V is the volume, n is the number of moles, R is the ideal gas constant, and T is the temperature.
In this case, the volume and temperature of the vessel remain constant, and we are interested in finding the partial pressure of helium when 5.0 moles of hydrogen are added. The initial conditions are:
Initial pressure = 7.0 atm
Initial moles of xenon = 3.0 moles
Initial moles of helium = 2.0 moles
Initial moles of hydrogen = 2.0 moles
To solve the problem, follow these steps:
1. Calculate the total moles of gas initially in the vessel:
Total moles = moles of xenon + moles of helium + moles of hydrogen
2. Calculate the partial pressure of each gas component initially:
Partial pressure = (moles of gas / total moles) * initial pressure
3. Calculate the total moles of gas after adding 5.0 moles of hydrogen:
Updated total moles = Total moles (initial) + moles added (5.0 moles)
4. Calculate the partial pressure of helium after adding 5.0 moles of hydrogen:
Partial pressure (helium) = (moles of helium / updated total moles) * initial pressure
The reason why the total pressure remains constant at 7.0 atm even after adding additional moles of hydrogen is because the volume and temperature are constant. According to Dalton's law of partial pressures, the total pressure in a mixture of gases is the sum of all the individual partial pressures of each gas in the mixture, assuming ideal gas behavior.